Class ActiveRecord::Base
In: vendor/rails/activerecord/lib/active_record/base.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb
Parent: Object

Active Record objects don‘t specify their attributes directly, but rather infer them from the table definition with which they‘re linked. Adding, removing, and changing attributes and their type is done directly in the database. Any change is instantly reflected in the Active Record objects. The mapping that binds a given Active Record class to a certain database table will happen automatically in most common cases, but can be overwritten for the uncommon ones.

See the mapping rules in table_name and the full example in files/README.html for more insight.

Creation

Active Records accept constructor parameters either in a hash or as a block. The hash method is especially useful when you‘re receiving the data from somewhere else, like an HTTP request. It works like this:

  user = User.new(:name => "David", :occupation => "Code Artist")
  user.name # => "David"

You can also use block initialization:

  user = User.new do |u|
    u.name = "David"
    u.occupation = "Code Artist"
  end

And of course you can just create a bare object and specify the attributes after the fact:

  user = User.new
  user.name = "David"
  user.occupation = "Code Artist"

Conditions

Conditions can either be specified as a string, array, or hash representing the WHERE-part of an SQL statement. The array form is to be used when the condition input is tainted and requires sanitization. The string form can be used for statements that don‘t involve tainted data. The hash form works much like the array form, except only equality and range is possible. Examples:

  class User < ActiveRecord::Base
    def self.authenticate_unsafely(user_name, password)
      find(:first, :conditions => "user_name = '#{user_name}' AND password = '#{password}'")
    end

    def self.authenticate_safely(user_name, password)
      find(:first, :conditions => [ "user_name = ? AND password = ?", user_name, password ])
    end

    def self.authenticate_safely_simply(user_name, password)
      find(:first, :conditions => { :user_name => user_name, :password => password })
    end
  end

The authenticate_unsafely method inserts the parameters directly into the query and is thus susceptible to SQL-injection attacks if the user_name and password parameters come directly from an HTTP request. The authenticate_safely and authenticate_safely_simply both will sanitize the user_name and password before inserting them in the query, which will ensure that an attacker can‘t escape the query and fake the login (or worse).

When using multiple parameters in the conditions, it can easily become hard to read exactly what the fourth or fifth question mark is supposed to represent. In those cases, you can resort to named bind variables instead. That‘s done by replacing the question marks with symbols and supplying a hash with values for the matching symbol keys:

  Company.find(:first, :conditions => [
    "id = :id AND name = :name AND division = :division AND created_at > :accounting_date",
    { :id => 3, :name => "37signals", :division => "First", :accounting_date => '2005-01-01' }
  ])

Similarly, a simple hash without a statement will generate conditions based on equality with the SQL AND operator. For instance:

  Student.find(:all, :conditions => { :first_name => "Harvey", :status => 1 })
  Student.find(:all, :conditions => params[:student])

A range may be used in the hash to use the SQL BETWEEN operator:

  Student.find(:all, :conditions => { :grade => 9..12 })

An array may be used in the hash to use the SQL IN operator:

  Student.find(:all, :conditions => { :grade => [9,11,12] })

Overwriting default accessors

All column values are automatically available through basic accessors on the Active Record object, but sometimes you want to specialize this behavior. This can be done by overwriting the default accessors (using the same name as the attribute) and calling read_attribute(attr_name) and write_attribute(attr_name, value) to actually change things. Example:

  class Song < ActiveRecord::Base
    # Uses an integer of seconds to hold the length of the song

    def length=(minutes)
      write_attribute(:length, minutes.to_i * 60)
    end

    def length
      read_attribute(:length) / 60
    end
  end

You can alternatively use self[:attribute]=(value) and self[:attribute] instead of write_attribute(:attribute, value) and read_attribute(:attribute) as a shorter form.

Attribute query methods

In addition to the basic accessors, query methods are also automatically available on the Active Record object. Query methods allow you to test whether an attribute value is present.

For example, an Active Record User with the name attribute has a name? method that you can call to determine whether the user has a name:

  user = User.new(:name => "David")
  user.name? # => true

  anonymous = User.new(:name => "")
  anonymous.name? # => false

Accessing attributes before they have been typecasted

Sometimes you want to be able to read the raw attribute data without having the column-determined typecast run its course first. That can be done by using the <attribute>_before_type_cast accessors that all attributes have. For example, if your Account model has a balance attribute, you can call account.balance_before_type_cast or account.id_before_type_cast.

This is especially useful in validation situations where the user might supply a string for an integer field and you want to display the original string back in an error message. Accessing the attribute normally would typecast the string to 0, which isn‘t what you want.

Dynamic attribute-based finders

Dynamic attribute-based finders are a cleaner way of getting (and/or creating) objects by simple queries without turning to SQL. They work by appending the name of an attribute to find_by_ or find_all_by_, so you get finders like Person.find_by_user_name, Person.find_all_by_last_name, and Payment.find_by_transaction_id. So instead of writing Person.find(:first, :conditions => ["user_name = ?", user_name]), you just do Person.find_by_user_name(user_name). And instead of writing Person.find(:all, :conditions => ["last_name = ?", last_name]), you just do Person.find_all_by_last_name(last_name).

It‘s also possible to use multiple attributes in the same find by separating them with "and", so you get finders like Person.find_by_user_name_and_password or even Payment.find_by_purchaser_and_state_and_country. So instead of writing Person.find(:first, :conditions => ["user_name = ? AND password = ?", user_name, password]), you just do Person.find_by_user_name_and_password(user_name, password).

It‘s even possible to use all the additional parameters to find. For example, the full interface for Payment.find_all_by_amount is actually Payment.find_all_by_amount(amount, options). And the full interface to Person.find_by_user_name is actually Person.find_by_user_name(user_name, options). So you could call Payment.find_all_by_amount(50, :order => "created_on").

The same dynamic finder style can be used to create the object if it doesn‘t already exist. This dynamic finder is called with find_or_create_by_ and will return the object if it already exists and otherwise creates it, then returns it. Protected attributes won‘t be set unless they are given in a block. For example:

  # No 'Summer' tag exists
  Tag.find_or_create_by_name("Summer") # equal to Tag.create(:name => "Summer")

  # Now the 'Summer' tag does exist
  Tag.find_or_create_by_name("Summer") # equal to Tag.find_by_name("Summer")

  # Now 'Bob' exist and is an 'admin'
  User.find_or_create_by_name('Bob', :age => 40) { |u| u.admin = true }

Use the find_or_initialize_by_ finder if you want to return a new record without saving it first. Protected attributes won‘t be setted unless they are given in a block. For example:

  # No 'Winter' tag exists
  winter = Tag.find_or_initialize_by_name("Winter")
  winter.new_record? # true

To find by a subset of the attributes to be used for instantiating a new object, pass a hash instead of a list of parameters. For example:

  Tag.find_or_create_by_name(:name => "rails", :creator => current_user)

That will either find an existing tag named "rails", or create a new one while setting the user that created it.

Saving arrays, hashes, and other non-mappable objects in text columns

Active Record can serialize any object in text columns using YAML. To do so, you must specify this with a call to the class method serialize. This makes it possible to store arrays, hashes, and other non-mappable objects without doing any additional work. Example:

  class User < ActiveRecord::Base
    serialize :preferences
  end

  user = User.create(:preferences => { "background" => "black", "display" => large })
  User.find(user.id).preferences # => { "background" => "black", "display" => large }

You can also specify a class option as the second parameter that‘ll raise an exception if a serialized object is retrieved as a descendent of a class not in the hierarchy. Example:

  class User < ActiveRecord::Base
    serialize :preferences, Hash
  end

  user = User.create(:preferences => %w( one two three ))
  User.find(user.id).preferences    # raises SerializationTypeMismatch

Single table inheritance

Active Record allows inheritance by storing the name of the class in a column that by default is named "type" (can be changed by overwriting Base.inheritance_column). This means that an inheritance looking like this:

  class Company < ActiveRecord::Base; end
  class Firm < Company; end
  class Client < Company; end
  class PriorityClient < Client; end

When you do Firm.create(:name => "37signals"), this record will be saved in the companies table with type = "Firm". You can then fetch this row again using Company.find(:first, "name = ‘37signals’") and it will return a Firm object.

If you don‘t have a type column defined in your table, single-table inheritance won‘t be triggered. In that case, it‘ll work just like normal subclasses with no special magic for differentiating between them or reloading the right type with find.

Note, all the attributes for all the cases are kept in the same table. Read more: www.martinfowler.com/eaaCatalog/singleTableInheritance.html

Connection to multiple databases in different models

Connections are usually created through ActiveRecord::Base.establish_connection and retrieved by ActiveRecord::Base.connection. All classes inheriting from ActiveRecord::Base will use this connection. But you can also set a class-specific connection. For example, if Course is an ActiveRecord::Base, but resides in a different database, you can just say Course.establish_connection and Course and all of its subclasses will use this connection instead.

This feature is implemented by keeping a connection pool in ActiveRecord::Base that is a Hash indexed by the class. If a connection is requested, the retrieve_connection method will go up the class-hierarchy until a connection is found in the connection pool.

Exceptions

Note: The attributes listed are class-level attributes (accessible from both the class and instance level). So it‘s possible to assign a logger to the class through Base.logger= which will then be used by all instances in the current object space.

Methods

==   ===   []   []=   abstract_class?   aggregate_mapping   all   attr_accessible   attr_protected   attr_readonly   attribute_for_inspect   attribute_names   attribute_present?   attributes   attributes=   attributes_before_type_cast   base_class   becomes   benchmark   cache_key   class_of_active_record_descendant   clear_active_connections!   clear_reloadable_connections!   clone   column_for_attribute   column_names   columns   columns_hash   compute_type   connected?   connection   connection   content_columns   count_by_sql   create   decrement   decrement!   decrement_counter   delete   delete_all   descends_from_active_record?   destroy   destroy   destroy_all   eql?   establish_connection   exists?   expand_hash_conditions_for_aggregates   find   find_by_sql   first   freeze   frozen?   has_attribute?   hash   id   id=   increment   increment!   increment_counter   inheritance_column   inspect   inspect   last   new   new_record?   primary_key   readonly!   readonly?   readonly_attributes   reload   remove_connection   require_mysql   reset_column_information   respond_to?   sanitize_sql_array   sanitize_sql_for_assignment   sanitize_sql_for_conditions   sanitize_sql_hash_for_assignment   sanitize_sql_hash_for_conditions   save   save!   serialize   serialized_attributes   set_inheritance_column   set_primary_key   set_sequence_name   set_table_name   silence   sti_name   table_exists?   table_name   to_param   toggle   toggle!   update   update_all   update_attribute   update_attributes   update_attributes!   update_counters   with_exclusive_scope   with_scope  

Constants

VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset, :order, :select, :readonly, :group, :from, :lock ]

External Aliases

set_table_name -> table_name=
set_primary_key -> primary_key=
set_inheritance_column -> inheritance_column=
set_sequence_name -> sequence_name=
sanitize_sql_for_conditions -> sanitize_sql
sanitize_sql_hash_for_conditions -> sanitize_sql_hash
sanitize_sql -> sanitize_conditions

Attributes

abstract_class  [RW]  Set this to true if this is an abstract class (see abstract_class?).

Public Class methods

Overwrite the default class equality method to provide support for association proxies.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1269
1269:       def ===(object)
1270:         object.is_a?(self)
1271:       end

Returns whether this class is a base AR class. If A is a base class and B descends from A, then B.base_class will return B.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1285
1285:       def abstract_class?
1286:         defined?(@abstract_class) && @abstract_class == true
1287:       end

This is an alias for find(:all). You can pass in all the same arguments to this method as you can to find(:all)

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 555
555:       def all(*args)
556:         find(:all, *args)
557:       end

Specifies a white list of model attributes that can be set via mass-assignment, such as new(attributes), update_attributes(attributes), or attributes=(attributes)

This is the opposite of the attr_protected macro: Mass-assignment will only set attributes in this list, to assign to the rest of attributes you can use direct writer methods. This is meant to protect sensitive attributes from being overwritten by malicious users tampering with URLs or forms. If you‘d rather start from an all-open default and restrict attributes as needed, have a look at attr_protected.

  class Customer < ActiveRecord::Base
    attr_accessible :name, :nickname
  end

  customer = Customer.new(:name => "David", :nickname => "Dave", :credit_rating => "Excellent")
  customer.credit_rating # => nil
  customer.attributes = { :name => "Jolly fellow", :credit_rating => "Superb" }
  customer.credit_rating # => nil

  customer.credit_rating = "Average"
  customer.credit_rating # => "Average"

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 930
930:       def attr_accessible(*attributes)
931:         write_inheritable_attribute("attr_accessible", Set.new(attributes.map(&:to_s)) + (accessible_attributes || []))
932:       end

Attributes named in this macro are protected from mass-assignment, such as new(attributes), update_attributes(attributes), or attributes=(attributes).

Mass-assignment to these attributes will simply be ignored, to assign to them you can use direct writer methods. This is meant to protect sensitive attributes from being overwritten by malicious users tampering with URLs or forms.

  class Customer < ActiveRecord::Base
    attr_protected :credit_rating
  end

  customer = Customer.new("name" => David, "credit_rating" => "Excellent")
  customer.credit_rating # => nil
  customer.attributes = { "description" => "Jolly fellow", "credit_rating" => "Superb" }
  customer.credit_rating # => nil

  customer.credit_rating = "Average"
  customer.credit_rating # => "Average"

To start from an all-closed default and enable attributes as needed, have a look at attr_accessible.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 897
897:       def attr_protected(*attributes)
898:         write_inheritable_attribute("attr_protected", Set.new(attributes.map(&:to_s)) + (protected_attributes || []))
899:       end

Attributes listed as readonly can be set for a new record, but will be ignored in database updates afterwards.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 940
940:        def attr_readonly(*attributes)
941:          write_inheritable_attribute("attr_readonly", Set.new(attributes.map(&:to_s)) + (readonly_attributes || []))
942:        end

Returns the base AR subclass that this class descends from. If A extends AR::Base, A.base_class will return A. If B descends from A through some arbitrarily deep hierarchy, B.base_class will return A.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1276
1276:       def base_class
1277:         class_of_active_record_descendant(self)
1278:       end

Log and benchmark multiple statements in a single block. Example:

  Project.benchmark("Creating project") do
    project = Project.create("name" => "stuff")
    project.create_manager("name" => "David")
    project.milestones << Milestone.find(:all)
  end

The benchmark is only recorded if the current level of the logger is less than or equal to the log_level, which makes it easy to include benchmarking statements in production software that will remain inexpensive because the benchmark will only be conducted if the log level is low enough.

The logging of the multiple statements is turned off unless use_silence is set to false.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1249
1249:       def benchmark(title, log_level = Logger::DEBUG, use_silence = true)
1250:         if logger && logger.level <= log_level
1251:           result = nil
1252:           seconds = Benchmark.realtime { result = use_silence ? silence { yield } : yield }
1253:           logger.add(log_level, "#{title} (#{'%.5f' % seconds})")
1254:           result
1255:         else
1256:           yield
1257:         end
1258:       end

Clears the cache which maps classes to connections.

[Source]

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 84
84:       def clear_active_connections!
85:         clear_cache!(@@active_connections) do |name, conn|
86:           conn.disconnect!
87:         end
88:       end

Clears the cache which maps classes

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 91
 91:       def clear_reloadable_connections!
 92:         if @@allow_concurrency
 93:           # With concurrent connections @@active_connections is
 94:           # a hash keyed by thread id.
 95:           @@active_connections.each do |thread_id, conns|
 96:             conns.each do |name, conn|
 97:               if conn.requires_reloading?
 98:                 conn.disconnect!
 99:                 @@active_connections[thread_id].delete(name)
100:               end
101:             end
102:           end
103:         else
104:           @@active_connections.each do |name, conn|
105:             if conn.requires_reloading?
106:               conn.disconnect!
107:               @@active_connections.delete(name)
108:             end
109:           end
110:         end
111:       end

Returns an array of column names as strings.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1157
1157:       def column_names
1158:         @column_names ||= columns.map { |column| column.name }
1159:       end

Returns an array of column objects for the table associated with this class.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1143
1143:       def columns
1144:         unless defined?(@columns) && @columns
1145:           @columns = connection.columns(table_name, "#{name} Columns")
1146:           @columns.each { |column| column.primary = column.name == primary_key }
1147:         end
1148:         @columns
1149:       end

Returns a hash of column objects for the table associated with this class.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1152
1152:       def columns_hash
1153:         @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash }
1154:       end

Returns true if a connection that‘s accessible to this class has already been opened.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 269
269:     def self.connected?
270:       active_connections[active_connection_name] ? true : false
271:     end

Returns the connection currently associated with the class. This can also be used to "borrow" the connection to do database work unrelated to any of the specific Active Records.

[Source]

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 73
73:       def connection
74:         if defined?(@active_connection_name) && (conn = active_connections[@active_connection_name])
75:           conn
76:         else
77:           # retrieve_connection sets the cache key.
78:           conn = retrieve_connection
79:           active_connections[@active_connection_name] = conn
80:         end
81:       end

Returns an array of column objects where the primary id, all columns ending in "_id" or "_count", and columns used for single table inheritance have been removed.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1163
1163:       def content_columns
1164:         @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
1165:       end

Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part. The use of this method should be restricted to complicated SQL queries that can‘t be executed using the ActiveRecord::Calculations class methods. Look into those before using this.

Attributes

  • sql - An SQL statement which should return a count query from the database, see the example below.

Examples

  Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id = c.id"

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 801
801:       def count_by_sql(sql)
802:         sql = sanitize_conditions(sql)
803:         connection.select_value(sql, "#{name} Count").to_i
804:       end

Creates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.

The attributes parameter can be either be a Hash or an Array of Hashes. These Hashes describe the attributes on the objects that are to be created.

Examples

  # Create a single new object
  User.create(:first_name => 'Jamie')

  # Create an Array of new objects
  User.create([{ :first_name => 'Jamie' }, { :first_name => 'Jeremy' }])

  # Create a single object and pass it into a block to set other attributes.
  User.create(:first_name => 'Jamie') do |u|
    u.is_admin = false
  end

  # Creating an Array of new objects using a block, where the block is executed for each object:
  User.create([{ :first_name => 'Jamie' }, { :first_name => 'Jeremy' }]) do |u|
    u.is_admin = false
  end

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 634
634:       def create(attributes = nil, &block)
635:         if attributes.is_a?(Array)
636:           attributes.collect { |attr| create(attr, &block) }
637:         else
638:           object = new(attributes)
639:           yield(object) if block_given?
640:           object.save
641:           object
642:         end
643:       end

Decrement a number field by one, usually representing a count.

This works the same as increment_counter but reduces the column value by 1 instead of increasing it.

Attributes

  • counter_name - The name of the field that should be decremented.
  • id - The id of the object that should be decremented.

Examples

  # Decrement the post_count column for the record with an id of 5
  DiscussionBoard.decrement_counter(:post_count, 5)

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 868
868:       def decrement_counter(counter_name, id)
869:         update_counters(id, counter_name => -1)
870:       end

Delete an object (or multiple objects) where the id given matches the primary_key. A SQL DELETE command is executed on the database which means that no callbacks are fired off running this. This is an efficient method of deleting records that don‘t need cleaning up after or other actions to be taken.

Objects are not instantiated with this method.

Attributes

  • id - Can be either an Integer or an Array of Integers.

Examples

  # Delete a single object
  Todo.delete(1)

  # Delete multiple objects
  todos = [1,2,3]
  Todo.delete(todos)

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 690
690:       def delete(id)
691:         delete_all([ "#{connection.quote_column_name(primary_key)} IN (?)", id ])
692:       end

Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method and invoking callbacks. This is a single SQL query, much more efficient than destroy_all.

Attributes

  • conditions - Conditions are specified the same way as with find method.

Example

  Post.delete_all "person_id = 5 AND (category = 'Something' OR category = 'Else')"

This deletes the affected posts all at once with a single DELETE query. If you need to destroy dependent associations or call your before_ or after_destroy callbacks, use the destroy_all method instead.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 784
784:       def delete_all(conditions = nil)
785:         sql = "DELETE FROM #{quoted_table_name} "
786:         add_conditions!(sql, conditions, scope(:find))
787:         connection.delete(sql, "#{name} Delete all")
788:       end

True if this isn‘t a concrete subclass needing a STI type condition.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1199
1199:       def descends_from_active_record?
1200:         if superclass.abstract_class?
1201:           superclass.descends_from_active_record?
1202:         else
1203:           superclass == Base || !columns_hash.include?(inheritance_column)
1204:         end
1205:       end

Destroy an object (or multiple objects) that has the given id, the object is instantiated first, therefore all callbacks and filters are fired off before the object is deleted. This method is less efficient than ActiveRecord#delete but allows cleanup methods and other actions to be run.

This essentially finds the object (or multiple objects) with the given id, creates a new object from the attributes, and then calls destroy on it.

Attributes

  • id - Can be either an Integer or an Array of Integers.

Examples

  # Destroy a single object
  Todo.destroy(1)

  # Destroy multiple objects
  todos = [1,2,3]
  Todo.destroy(todos)

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 713
713:       def destroy(id)
714:         if id.is_a?(Array)
715:           id.map { |one_id| destroy(one_id) }
716:         else
717:           find(id).destroy
718:         end
719:       end

Destroys the records matching conditions by instantiating each record and calling the destroy method. This means at least 2*N database queries to destroy N records, so avoid destroy_all if you are deleting many records. If you want to simply delete records without worrying about dependent associations or callbacks, use the much faster delete_all method instead.

Attributes

  • conditions - Conditions are specified the same way as with find method.

Example

  Person.destroy_all "last_login < '2004-04-04'"

This loads and destroys each person one by one, including its dependent associations and before_ and after_destroy callbacks.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 766
766:       def destroy_all(conditions = nil)
767:         find(:all, :conditions => conditions).each { |object| object.destroy }
768:       end

Establishes the connection to the database. Accepts a hash as input where the :adapter key must be specified with the name of a database adapter (in lower-case) example for regular databases (MySQL, Postgresql, etc):

  ActiveRecord::Base.establish_connection(
    :adapter  => "mysql",
    :host     => "localhost",
    :username => "myuser",
    :password => "mypass",
    :database => "somedatabase"
  )

Example for SQLite database:

  ActiveRecord::Base.establish_connection(
    :adapter => "sqlite",
    :database  => "path/to/dbfile"
  )

Also accepts keys as strings (for parsing from YAML for example):

  ActiveRecord::Base.establish_connection(
    "adapter" => "sqlite",
    "database"  => "path/to/dbfile"
  )

The exceptions AdapterNotSpecified, AdapterNotFound and ArgumentError may be returned on an error.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 205
205:     def self.establish_connection(spec = nil)
206:       case spec
207:         when nil
208:           raise AdapterNotSpecified unless defined? RAILS_ENV
209:           establish_connection(RAILS_ENV)
210:         when ConnectionSpecification
211:           clear_active_connection_name
212:           @active_connection_name = name
213:           @@defined_connections[name] = spec
214:         when Symbol, String
215:           if configuration = configurations[spec.to_s]
216:             establish_connection(configuration)
217:           else
218:             raise AdapterNotSpecified, "#{spec} database is not configured"
219:           end
220:         else
221:           spec = spec.symbolize_keys
222:           unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
223: 
224:           begin
225:             require 'rubygems'
226:             gem "activerecord-#{spec[:adapter]}-adapter"
227:             require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
228:           rescue LoadError
229:             begin
230:               require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
231:             rescue LoadError
232:               raise "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{$!})"
233:             end
234:           end
235: 
236:           adapter_method = "#{spec[:adapter]}_connection"
237:           if !respond_to?(adapter_method)
238:             raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter"
239:           end
240: 
241:           remove_connection
242:           establish_connection(ConnectionSpecification.new(spec, adapter_method))
243:       end
244:     end

Checks whether a record exists in the database that matches conditions given. These conditions can either be a single integer representing a primary key id to be found, or a condition to be matched like using ActiveRecord#find.

The id_or_conditions parameter can be an Integer or a String if you want to search the primary key column of the table for a matching id, or if you‘re looking to match against a condition you can use an Array or a Hash.

Possible gotcha: You can‘t pass in a condition as a string e.g. "name = ‘Jamie’", this would be sanitized and then queried against the primary key column as "id = ‘name = \’Jamie"

Examples

  Person.exists?(5)
  Person.exists?('5')
  Person.exists?(:name => "David")
  Person.exists?(['name LIKE ?', "%#{query}%"])

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 601
601:       def exists?(id_or_conditions)
602:         connection.select_all(
603:           construct_finder_sql(
604:             :select     => "#{quoted_table_name}.#{primary_key}",
605:             :conditions => expand_id_conditions(id_or_conditions),
606:             :limit      => 1
607:           ),
608:           "#{name} Exists"
609:         ).size > 0
610:       end

Find operates with four different retrieval approaches:

  • Find by id - This can either be a specific id (1), a list of ids (1, 5, 6), or an array of ids ([5, 6, 10]). If no record can be found for all of the listed ids, then RecordNotFound will be raised.
  • Find first - This will return the first record matched by the options used. These options can either be specific conditions or merely an order. If no record can be matched, nil is returned. Use Model.find(:first, *args) or its shortcut Model.first(*args).
  • Find last - This will return the last record matched by the options used. These options can either be specific conditions or merely an order. If no record can be matched, nil is returned. Use Model.find(:last, *args) or its shortcut Model.last(*args).
  • Find all - This will return all the records matched by the options used. If no records are found, an empty array is returned. Use Model.find(:all, *args) or its shortcut Model.all(*args).

All approaches accept an options hash as their last parameter.

Attributes

  • :conditions - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro.
  • :order - An SQL fragment like "created_at DESC, name".
  • :group - An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
  • :limit - An integer determining the limit on the number of rows that should be returned.
  • :offset - An integer determining the offset from where the rows should be fetched. So at 5, it would skip rows 0 through 4.
  • :joins - Either an SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id" (rarely needed) or named associations in the same form used for the :include option, which will perform an INNER JOIN on the associated table(s). If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table‘s columns. Pass :readonly => false to override.
  • :include - Names associations that should be loaded alongside. The symbols named refer to already defined associations. See eager loading under Associations.
  • :select - By default, this is "*" as in "SELECT * FROM", but can be changed if you, for example, want to do a join but not include the joined columns.
  • :from - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name of a database view).
  • :readonly - Mark the returned records read-only so they cannot be saved or updated.
  • :lock - An SQL fragment like "FOR UPDATE" or "LOCK IN SHARE MODE". :lock => true gives connection‘s default exclusive lock, usually "FOR UPDATE".

Examples

  # find by id
  Person.find(1)       # returns the object for ID = 1
  Person.find(1, 2, 6) # returns an array for objects with IDs in (1, 2, 6)
  Person.find([7, 17]) # returns an array for objects with IDs in (7, 17)
  Person.find([1])     # returns an array for the object with ID = 1
  Person.find(1, :conditions => "administrator = 1", :order => "created_on DESC")

Note that returned records may not be in the same order as the ids you provide since database rows are unordered. Give an explicit :order to ensure the results are sorted.

Examples

  # find first
  Person.find(:first) # returns the first object fetched by SELECT * FROM people
  Person.find(:first, :conditions => [ "user_name = ?", user_name])
  Person.find(:first, :order => "created_on DESC", :offset => 5)

  # find last
  Person.find(:last) # returns the last object fetched by SELECT * FROM people
  Person.find(:last, :conditions => [ "user_name = ?", user_name])
  Person.find(:last, :order => "created_on DESC", :offset => 5)

  # find all
  Person.find(:all) # returns an array of objects for all the rows fetched by SELECT * FROM people
  Person.find(:all, :conditions => [ "category IN (?)", categories], :limit => 50)
  Person.find(:all, :conditions => { :friends => ["Bob", "Steve", "Fred"] }
  Person.find(:all, :offset => 10, :limit => 10)
  Person.find(:all, :include => [ :account, :friends ])
  Person.find(:all, :group => "category")

Example for find with a lock: Imagine two concurrent transactions: each will read person.visits == 2, add 1 to it, and save, resulting in two saves of person.visits = 3. By locking the row, the second transaction has to wait until the first is finished; we get the expected person.visits == 4.

  Person.transaction do
    person = Person.find(1, :lock => true)
    person.visits += 1
    person.save!
  end

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 528
528:       def find(*args)
529:         options = args.extract_options!
530:         validate_find_options(options)
531:         set_readonly_option!(options)
532: 
533:         case args.first
534:           when :first then find_initial(options)
535:           when :last  then find_last(options)
536:           when :all   then find_every(options)
537:           else             find_from_ids(args, options)
538:         end
539:       end

Executes a custom SQL query against your database and returns all the results. The results will be returned as an array with columns requested encapsulated as attributes of the model you call this method from. If you call +Product.find_by_sql+ then the results will be returned in a Product object with the attributes you specified in the SQL query.

If you call a complicated SQL query which spans multiple tables the columns specified by the SELECT will be attributes of the model, whether or not they are columns of the corresponding table.

The sql parameter is a full SQL query as a string. It will be called as is, there will be no database agnostic conversions performed. This should be a last resort because using, for example, MySQL specific terms will lock you to using that particular database engine or require you to change your call if you switch engines

Examples

  # A simple SQL query spanning multiple tables
  Post.find_by_sql "SELECT p.title, c.author FROM posts p, comments c WHERE p.id = c.post_id"
  > [#<Post:0x36bff9c @attributes={"title"=>"Ruby Meetup", "first_name"=>"Quentin"}>, ...]

  # You can use the same string replacement techniques as you can with ActiveRecord#find
  Post.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]
  > [#<Post:0x36bff9c @attributes={"first_name"=>"The Cheap Man Buys Twice"}>, ...]

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 581
581:       def find_by_sql(sql)
582:         connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
583:       end

A convenience wrapper for find(:first, *args). You can pass in all the same arguments to this method as you can to find(:first).

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 543
543:       def first(*args)
544:         find(:first, *args)
545:       end

Increment a number field by one, usually representing a count.

This is used for caching aggregate values, so that they don‘t need to be computed every time. For example, a DiscussionBoard may cache post_count and comment_count otherwise every time the board is shown it would have to run an SQL query to find how many posts and comments there are.

Attributes

  • counter_name - The name of the field that should be incremented.
  • id - The id of the object that should be incremented.

Examples

  # Increment the post_count column for the record with an id of 5
  DiscussionBoard.increment_counter(:post_count, 5)

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 851
851:       def increment_counter(counter_name, id)
852:         update_counters(id, counter_name => 1)
853:       end

Defines the column name for use with single table inheritance — can be set in subclasses like so: self.inheritance_column = "type_id"

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1057
1057:       def inheritance_column
1058:         @inheritance_column ||= "type".freeze
1059:       end

Returns a string like ‘Post id:integer, title:string, body:text‘

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1213
1213:       def inspect
1214:         if self == Base
1215:           super
1216:         elsif abstract_class?
1217:           "#{super}(abstract)"
1218:         elsif table_exists?
1219:           attr_list = columns.map { |c| "#{c.name}: #{c.type}" } * ', '
1220:           "#{super}(#{attr_list})"
1221:         else
1222:           "#{super}(Table doesn't exist)"
1223:         end
1224:       end

A convenience wrapper for find(:last, *args). You can pass in all the same arguments to this method as you can to find(:last).

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 549
549:       def last(*args)
550:         find(:last, *args)
551:       end

New objects can be instantiated as either empty (pass no construction parameter) or pre-set with attributes but not yet saved (pass a hash with key names matching the associated table column names). In both instances, valid attribute keys are determined by the column names of the associated table — hence you can‘t have attributes that aren‘t part of the table columns.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2125
2125:       def initialize(attributes = nil)
2126:         @attributes = attributes_from_column_definition
2127:         @attributes_cache = {}
2128:         @new_record = true
2129:         ensure_proper_type
2130:         self.attributes = attributes unless attributes.nil?
2131:         self.class.send(:scope, :create).each { |att,value| self.send("#{att}=", value) } if self.class.send(:scoped?, :create)
2132:         result = yield self if block_given?
2133:         callback(:after_initialize) if respond_to_without_attributes?(:after_initialize)
2134:         result
2135:       end

Defines the primary key field — can be overridden in subclasses. Overwriting will negate any effect of the primary_key_prefix_type setting, though.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1034
1034:       def primary_key
1035:         reset_primary_key
1036:       end

Returns an array of all the attributes that have been specified as readonly.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 945
945:        def readonly_attributes
946:          read_inheritable_attribute("attr_readonly")
947:        end

Remove the connection for this class. This will close the active connection and the defined connection (if they exist). The result can be used as an argument for establish_connection, for easily re-establishing the connection.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 277
277:     def self.remove_connection(klass=self)
278:       spec = @@defined_connections[klass.name]
279:       konn = active_connections[klass.name]
280:       @@defined_connections.delete_if { |key, value| value == spec }
281:       active_connections.delete_if { |key, value| value == konn }
282:       konn.disconnect! if konn
283:       spec.config if spec
284:     end

[Source]

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb, line 47
47:     def self.require_mysql
48:       # Include the MySQL driver if one hasn't already been loaded
49:       unless defined? Mysql
50:         begin
51:           require_library_or_gem 'mysql'
52:         rescue LoadError => cannot_require_mysql
53:           # Use the bundled Ruby/MySQL driver if no driver is already in place
54:           begin
55:             ActiveRecord::Base.logger.info(
56:               "WARNING: You're using the Ruby-based MySQL library that ships with Rails. This library is not suited for production. " +
57:               "Please install the C-based MySQL library instead (gem install mysql)."
58:             ) if ActiveRecord::Base.logger
59: 
60:             require 'active_record/vendor/mysql'
61:           rescue LoadError
62:             raise cannot_require_mysql
63:           end
64:         end
65:       end
66: 
67:       # Define Mysql::Result.all_hashes
68:       MysqlCompat.define_all_hashes_method!
69:     end

Resets all the cached information about columns, which will cause them to be reloaded on the next request.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1182
1182:       def reset_column_information
1183:         generated_methods.each { |name| undef_method(name) }
1184:         @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @generated_methods = @inheritance_column = nil
1185:       end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1289
1289:       def respond_to?(method_id, include_private = false)
1290:         if match = matches_dynamic_finder?(method_id) || matches_dynamic_finder_with_initialize_or_create?(method_id)
1291:           return true if all_attributes_exists?(extract_attribute_names_from_match(match))
1292:         end
1293:         super
1294:       end

If you have an attribute that needs to be saved to the database as an object, and retrieved as the same object, then specify the name of that attribute using this method and it will be handled automatically. The serialization is done through YAML. If class_name is specified, the serialized object must be of that class on retrieval or SerializationTypeMismatch will be raised.

Attributes

  • attr_name - The field name that should be serialized.
  • class_name - Optional, class name that the object type should be equal to.

Example

  # Serialize a preferences attribute
  class User
    serialize :preferences
  end

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 964
964:       def serialize(attr_name, class_name = Object)
965:         serialized_attributes[attr_name.to_s] = class_name
966:       end

Returns a hash of all the attributes that have been specified for serialization as keys and their class restriction as values.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 969
969:       def serialized_attributes
970:         read_inheritable_attribute("attr_serialized") or write_inheritable_attribute("attr_serialized", {})
971:       end

Sets the name of the inheritance column to use to the given value, or (if the value # is nil or false) to the value returned by the given block.

  class Project < ActiveRecord::Base
    set_inheritance_column do
      original_inheritance_column + "_id"
    end
  end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1105
1105:       def set_inheritance_column(value = nil, &block)
1106:         define_attr_method :inheritance_column, value, &block
1107:       end

Sets the name of the primary key column to use to the given value, or (if the value is nil or false) to the value returned by the given block.

  class Project < ActiveRecord::Base
    set_primary_key "sysid"
  end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1091
1091:       def set_primary_key(value = nil, &block)
1092:         define_attr_method :primary_key, value, &block
1093:       end

Sets the name of the sequence to use when generating ids to the given value, or (if the value is nil or false) to the value returned by the given block. This is required for Oracle and is useful for any database which relies on sequences for primary key generation.

If a sequence name is not explicitly set when using Oracle or Firebird, it will default to the commonly used pattern of: #{table_name}_seq

If a sequence name is not explicitly set when using PostgreSQL, it will discover the sequence corresponding to your primary key for you.

  class Project < ActiveRecord::Base
    set_sequence_name "projectseq"   # default would have been "project_seq"
  end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1124
1124:       def set_sequence_name(value = nil, &block)
1125:         define_attr_method :sequence_name, value, &block
1126:       end

Sets the table name to use to the given value, or (if the value is nil or false) to the value returned by the given block.

  class Project < ActiveRecord::Base
    set_table_name "project"
  end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1079
1079:       def set_table_name(value = nil, &block)
1080:         define_attr_method :table_name, value, &block
1081:       end

Silences the logger for the duration of the block.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1261
1261:       def silence
1262:         old_logger_level, logger.level = logger.level, Logger::ERROR if logger
1263:         yield
1264:       ensure
1265:         logger.level = old_logger_level if logger
1266:       end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1296
1296:       def sti_name
1297:         store_full_sti_class ? name : name.demodulize
1298:       end

Indicates whether the table associated with this class exists

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1138
1138:       def table_exists?
1139:         connection.table_exists?(table_name)
1140:       end

Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from ActiveRecord::Base. So if the hierarchy looks like: Reply < Message < ActiveRecord::Base, then Message is used to guess the table name even when called on Reply. The rules used to do the guess are handled by the Inflector class in Active Support, which knows almost all common English inflections. You can add new inflections in config/initializers/inflections.rb.

Nested classes are given table names prefixed by the singular form of the parent‘s table name. Enclosing modules are not considered.

Examples

  class Invoice < ActiveRecord::Base; end;
  file                  class               table_name
  invoice.rb            Invoice             invoices

  class Invoice < ActiveRecord::Base; class Lineitem < ActiveRecord::Base; end; end;
  file                  class               table_name
  invoice.rb            Invoice::Lineitem   invoice_lineitems

  module Invoice; class Lineitem < ActiveRecord::Base; end; end;
  file                  class               table_name
  invoice/lineitem.rb   Invoice::Lineitem   lineitems

Additionally, the class-level table_name_prefix is prepended and the table_name_suffix is appended. So if you have "myapp_" as a prefix, the table name guess for an Invoice class becomes "myapp_invoices". Invoice::Lineitem becomes "myapp_invoice_lineitems".

You can also overwrite this class method to allow for unguessable links, such as a Mouse class with a link to a "mice" table. Example:

  class Mouse < ActiveRecord::Base
    set_table_name "mice"
  end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1007
1007:       def table_name
1008:         reset_table_name
1009:       end

Updates an object (or multiple objects) and saves it to the database, if validations pass. The resulting object is returned whether the object was saved successfully to the database or not.

Attributes

  • id - This should be the id or an array of ids to be updated.
  • attributes - This should be a Hash of attributes to be set on the object, or an array of Hashes.

Examples

  # Updating one record:
  Person.update(15, { :user_name => 'Samuel', :group => 'expert' })

  # Updating multiple records:
  people = { 1 => { "first_name" => "David" }, 2 => { "first_name" => "Jeremy" } }
  Person.update(people.keys, people.values)

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 661
661:       def update(id, attributes)
662:         if id.is_a?(Array)
663:           idx = -1
664:           id.collect { |one_id| idx += 1; update(one_id, attributes[idx]) }
665:         else
666:           object = find(id)
667:           object.update_attributes(attributes)
668:           object
669:         end
670:       end

Updates all records with details given if they match a set of conditions supplied, limits and order can also be supplied.

Attributes

  • updates - A String of column and value pairs that will be set on any records that match conditions.
  • conditions - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro for more info.
  • options - Additional options are :limit and/or :order, see the examples for usage.

Examples

  # Update all billing objects with the 3 different attributes given
  Billing.update_all( "category = 'authorized', approved = 1, author = 'David'" )

  # Update records that match our conditions
  Billing.update_all( "author = 'David'", "title LIKE '%Rails%'" )

  # Update records that match our conditions but limit it to 5 ordered by date
  Billing.update_all( "author = 'David'", "title LIKE '%Rails%'",
                        :order => 'created_at', :limit => 5 )

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 742
742:       def update_all(updates, conditions = nil, options = {})
743:         sql  = "UPDATE #{quoted_table_name} SET #{sanitize_sql_for_assignment(updates)} "
744:         scope = scope(:find)
745:         add_conditions!(sql, conditions, scope)
746:         add_order!(sql, options[:order], nil)
747:         add_limit!(sql, options, nil)
748:         connection.update(sql, "#{name} Update")
749:       end

A generic "counter updater" implementation, intended primarily to be used by increment_counter and decrement_counter, but which may also be useful on its own. It simply does a direct SQL update for the record with the given ID, altering the given hash of counters by the amount given by the corresponding value:

Attributes

  • id - The id of the object you wish to update a counter on.
  • counters - An Array of Hashes containing the names of the fields to update as keys and the amount to update the field by as values.

Examples

  # For the Post with id of 5, decrement the comment_count by 1, and
  # increment the action_count by 1
  Post.update_counters 5, :comment_count => -1, :action_count => 1
  # Executes the following SQL:
  # UPDATE posts
  #    SET comment_count = comment_count - 1,
  #        action_count = action_count + 1
  #  WHERE id = 5

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 828
828:       def update_counters(id, counters)
829:         updates = counters.inject([]) { |list, (counter_name, increment)|
830:           sign = increment < 0 ? "-" : "+"
831:           list << "#{connection.quote_column_name(counter_name)} = #{connection.quote_column_name(counter_name)} #{sign} #{increment.abs}"
832:         }.join(", ")
833:         update_all(updates, "#{connection.quote_column_name(primary_key)} = #{quote_value(id)}")
834:       end

Protected Class methods

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1956
1956:         def aggregate_mapping(reflection)
1957:           mapping = reflection.options[:mapping] || [reflection.name, reflection.name]
1958:           mapping.first.is_a?(Array) ? mapping : [mapping]
1959:         end

Returns the class descending directly from Active Record in the inheritance hierarchy.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1914
1914:         def class_of_active_record_descendant(klass)
1915:           if klass.superclass == Base || klass.superclass.abstract_class?
1916:             klass
1917:           elsif klass.superclass.nil?
1918:             raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
1919:           else
1920:             class_of_active_record_descendant(klass.superclass)
1921:           end
1922:         end

Returns the class type of the record using the current module as a prefix. So descendents of MyApp::Business::Account would appear as MyApp::Business::AccountSubclass.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1904
1904:         def compute_type(type_name)
1905:           modularized_name = type_name_with_module(type_name)
1906:           begin
1907:             class_eval(modularized_name, __FILE__, __LINE__)
1908:           rescue NameError
1909:             class_eval(type_name, __FILE__, __LINE__)
1910:           end
1911:         end

Accepts a hash of SQL conditions and replaces those attributes that correspond to a composed_of relationship with their expanded aggregate attribute values. Given:

    class Person < ActiveRecord::Base
      composed_of :address, :class_name => "Address",
        :mapping => [%w(address_street street), %w(address_city city)]
    end

Then:

    { :address => Address.new("813 abc st.", "chicago") }
      # => { :address_street => "813 abc st.", :address_city => "chicago" }

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1972
1972:         def expand_hash_conditions_for_aggregates(attrs)
1973:           expanded_attrs = {}
1974:           attrs.each do |attr, value|
1975:             unless (aggregation = reflect_on_aggregation(attr.to_sym)).nil?
1976:               mapping = aggregate_mapping(aggregation)
1977:               mapping.each do |field_attr, aggregate_attr|
1978:                 if mapping.size == 1 && !value.respond_to?(aggregate_attr)
1979:                   expanded_attrs[field_attr] = value
1980:                 else
1981:                   expanded_attrs[field_attr] = value.send(aggregate_attr)
1982:                 end
1983:               end
1984:             else
1985:               expanded_attrs[attr] = value
1986:             end
1987:           end
1988:           expanded_attrs
1989:         end

Accepts an array of conditions. The array has each value sanitized and interpolated into the SQL statement.

  ["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2036
2036:         def sanitize_sql_array(ary)
2037:           statement, *values = ary
2038:           if values.first.is_a?(Hash) and statement =~ /:\w+/
2039:             replace_named_bind_variables(statement, values.first)
2040:           elsif statement.include?('?')
2041:             replace_bind_variables(statement, values)
2042:           else
2043:             statement % values.collect { |value| connection.quote_string(value.to_s) }
2044:           end
2045:         end

Accepts an array, hash, or string of SQL conditions and sanitizes them into a valid SQL fragment for a SET clause.

  { :name => nil, :group_id => 4 }  returns "name = NULL , group_id='4'"

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1948
1948:         def sanitize_sql_for_assignment(assignments)
1949:           case assignments
1950:             when Array; sanitize_sql_array(assignments)
1951:             when Hash;  sanitize_sql_hash_for_assignment(assignments)
1952:             else        assignments
1953:           end
1954:         end

Accepts an array, hash, or string of SQL conditions and sanitizes them into a valid SQL fragment for a WHERE clause.

  ["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"
  { :name => "foo'bar", :group_id => 4 }  returns "name='foo''bar' and group_id='4'"
  "name='foo''bar' and group_id='4'" returns "name='foo''bar' and group_id='4'"

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1934
1934:         def sanitize_sql_for_conditions(condition)
1935:           return nil if condition.blank?
1936: 
1937:           case condition
1938:             when Array; sanitize_sql_array(condition)
1939:             when Hash;  sanitize_sql_hash_for_conditions(condition)
1940:             else        condition
1941:           end
1942:         end

Sanitizes a hash of attribute/value pairs into SQL conditions for a SET clause.

  { :status => nil, :group_id => 1 }
    # => "status = NULL , group_id = 1"

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2027
2027:         def sanitize_sql_hash_for_assignment(attrs)
2028:           attrs.map do |attr, value|
2029:             "#{connection.quote_column_name(attr)} = #{quote_bound_value(value)}"
2030:           end.join(', ')
2031:         end

Sanitizes a hash of attribute/value pairs into SQL conditions for a WHERE clause.

  { :name => "foo'bar", :group_id => 4 }
    # => "name='foo''bar' and group_id= 4"
  { :status => nil, :group_id => [1,2,3] }
    # => "status IS NULL and group_id IN (1,2,3)"
  { :age => 13..18 }
    # => "age BETWEEN 13 AND 18"
  { 'other_records.id' => 7 }
    # => "`other_records`.`id` = 7"

And for value objects on a composed_of relationship:

  { :address => Address.new("123 abc st.", "chicago") }
    # => "address_street='123 abc st.' and address_city='chicago'"

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2003
2003:         def sanitize_sql_hash_for_conditions(attrs)
2004:           attrs = expand_hash_conditions_for_aggregates(attrs)
2005: 
2006:           conditions = attrs.map do |attr, value|
2007:             attr = attr.to_s
2008: 
2009:             # Extract table name from qualified attribute names.
2010:             if attr.include?('.')
2011:               table_name, attr = attr.split('.', 2)
2012:               table_name = connection.quote_table_name(table_name)
2013:             else
2014:               table_name = quoted_table_name
2015:             end
2016: 
2017:             "#{table_name}.#{connection.quote_column_name(attr)} #{attribute_condition(value)}"
2018:           end.join(' AND ')
2019: 
2020:           replace_bind_variables(conditions, expand_range_bind_variables(attrs.values))
2021:         end

Works like with_scope, but discards any nested properties.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1859
1859:         def with_exclusive_scope(method_scoping = {}, &block)
1860:           with_scope(method_scoping, :overwrite, &block)
1861:         end

Scope parameters to method calls within the block. Takes a hash of method_name => parameters hash. method_name may be :find or :create. :find parameters may include the :conditions, :joins, :include, :offset, :limit, and :readonly options. :create parameters are an attributes hash.

  class Article < ActiveRecord::Base
    def self.create_with_scope
      with_scope(:find => { :conditions => "blog_id = 1" }, :create => { :blog_id => 1 }) do
        find(1) # => SELECT * from articles WHERE blog_id = 1 AND id = 1
        a = create(1)
        a.blog_id # => 1
      end
    end
  end

In nested scopings, all previous parameters are overwritten by the innermost rule, with the exception of :conditions and :include options in :find, which are merged.

  class Article < ActiveRecord::Base
    def self.find_with_scope
      with_scope(:find => { :conditions => "blog_id = 1", :limit => 1 }, :create => { :blog_id => 1 }) do
        with_scope(:find => { :limit => 10 })
          find(:all) # => SELECT * from articles WHERE blog_id = 1 LIMIT 10
        end
        with_scope(:find => { :conditions => "author_id = 3" })
          find(:all) # => SELECT * from articles WHERE blog_id = 1 AND author_id = 3 LIMIT 1
        end
      end
    end
  end

You can ignore any previous scopings by using the with_exclusive_scope method.

  class Article < ActiveRecord::Base
    def self.find_with_exclusive_scope
      with_scope(:find => { :conditions => "blog_id = 1", :limit => 1 }) do
        with_exclusive_scope(:find => { :limit => 10 })
          find(:all) # => SELECT * from articles LIMIT 10
        end
      end
    end
  end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1807
1807:         def with_scope(method_scoping = {}, action = :merge, &block)
1808:           method_scoping = method_scoping.method_scoping if method_scoping.respond_to?(:method_scoping)
1809: 
1810:           # Dup first and second level of hash (method and params).
1811:           method_scoping = method_scoping.inject({}) do |hash, (method, params)|
1812:             hash[method] = (params == true) ? params : params.dup
1813:             hash
1814:           end
1815: 
1816:           method_scoping.assert_valid_keys([ :find, :create ])
1817: 
1818:           if f = method_scoping[:find]
1819:             f.assert_valid_keys(VALID_FIND_OPTIONS)
1820:             set_readonly_option! f
1821:           end
1822: 
1823:           # Merge scopings
1824:           if action == :merge && current_scoped_methods
1825:             method_scoping = current_scoped_methods.inject(method_scoping) do |hash, (method, params)|
1826:               case hash[method]
1827:                 when Hash
1828:                   if method == :find
1829:                     (hash[method].keys + params.keys).uniq.each do |key|
1830:                       merge = hash[method][key] && params[key] # merge if both scopes have the same key
1831:                       if key == :conditions && merge
1832:                         hash[method][key] = merge_conditions(params[key], hash[method][key])
1833:                       elsif key == :include && merge
1834:                         hash[method][key] = merge_includes(hash[method][key], params[key]).uniq
1835:                       else
1836:                         hash[method][key] = hash[method][key] || params[key]
1837:                       end
1838:                     end
1839:                   else
1840:                     hash[method] = params.merge(hash[method])
1841:                   end
1842:                 else
1843:                   hash[method] = params
1844:               end
1845:               hash
1846:             end
1847:           end
1848: 
1849:           self.scoped_methods << method_scoping
1850: 
1851:           begin
1852:             yield
1853:           ensure
1854:             self.scoped_methods.pop
1855:           end
1856:         end

Public Instance methods

Returns true if the comparison_object is the same object, or is of the same type and has the same id.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2421
2421:       def ==(comparison_object)
2422:         comparison_object.equal?(self) ||
2423:           (comparison_object.instance_of?(self.class) &&
2424:             comparison_object.id == id &&
2425:             !comparison_object.new_record?)
2426:       end

Returns the value of the attribute identified by attr_name after it has been typecast (for example, "2004-12-12" in a data column is cast to a date object, like Date.new(2004, 12, 12)). (Alias for the protected read_attribute method).

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2338
2338:       def [](attr_name)
2339:         read_attribute(attr_name)
2340:       end

Updates the attribute identified by attr_name with the specified value. (Alias for the protected write_attribute method).

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2344
2344:       def []=(attr_name, value)
2345:         write_attribute(attr_name, value)
2346:       end

Format attributes nicely for inspect.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2386
2386:       def attribute_for_inspect(attr_name)
2387:         value = read_attribute(attr_name)
2388: 
2389:         if value.is_a?(String) && value.length > 50
2390:           "#{value[0..50]}...".inspect
2391:         elsif value.is_a?(Date) || value.is_a?(Time)
2392:           %("#{value.to_s(:db)}")
2393:         else
2394:           value.inspect
2395:         end
2396:       end

Returns an array of names for the attributes available on this object sorted alphabetically.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2411
2411:       def attribute_names
2412:         @attributes.keys.sort
2413:       end

Returns true if the specified attribute has been set by the user or by a database load and is neither nil nor empty? (the latter only applies to objects that respond to empty?, most notably Strings).

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2400
2400:       def attribute_present?(attribute)
2401:         value = read_attribute(attribute)
2402:         !value.blank?
2403:       end

Returns a hash of all the attributes with their names as keys and the values of the attributes as values.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2370
2370:       def attributes
2371:         self.attribute_names.inject({}) do |attrs, name|
2372:           attrs[name] = read_attribute(name)
2373:           attrs
2374:         end
2375:       end

Allows you to set all the attributes at once by passing in a hash with keys matching the attribute names (which again matches the column names). Sensitive attributes can be protected from this form of mass-assignment by using the attr_protected macro. Or you can alternatively specify which attributes can be accessed with the attr_accessible macro. Then all the attributes not included in that won‘t be allowed to be mass-assigned.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2353
2353:       def attributes=(new_attributes, guard_protected_attributes = true)
2354:         return if new_attributes.nil?
2355:         attributes = new_attributes.dup
2356:         attributes.stringify_keys!
2357: 
2358:         multi_parameter_attributes = []
2359:         attributes = remove_attributes_protected_from_mass_assignment(attributes) if guard_protected_attributes
2360: 
2361:         attributes.each do |k, v|
2362:           k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v)
2363:         end
2364: 
2365:         assign_multiparameter_attributes(multi_parameter_attributes)
2366:       end

Returns a hash of attributes before typecasting and deserialization.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2378
2378:       def attributes_before_type_cast
2379:         self.attribute_names.inject({}) do |attrs, name|
2380:           attrs[name] = read_attribute_before_type_cast(name)
2381:           attrs
2382:         end
2383:       end

Returns an instance of the specified klass with the attributes of the current record. This is mostly useful in relation to single-table inheritance structures where you want a subclass to appear as the superclass. This can be used along with record identification in Action Pack to allow, say, Client < Company to do something like render :partial => @client.becomes(Company) to render that instance using the companies/company partial instead of clients/client.

Note: The new instance will share a link to the same attributes as the original class. So any change to the attributes in either instance will affect the other.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2243
2243:       def becomes(klass)
2244:         returning klass.new do |became|
2245:           became.instance_variable_set("@attributes", @attributes)
2246:           became.instance_variable_set("@attributes_cache", @attributes_cache)
2247:           became.instance_variable_set("@new_record", new_record?)
2248:         end
2249:       end

Returns a cache key that can be used to identify this record.

Examples

  Product.new.cache_key     # => "products/new"
  Product.find(5).cache_key # => "products/5" (updated_at not available)
  Person.find(5).cache_key  # => "people/5-20071224150000" (updated_at available)

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2162
2162:       def cache_key
2163:         case
2164:         when new_record?
2165:           "#{self.class.name.tableize}/new"
2166:         when self[:updated_at]
2167:           "#{self.class.name.tableize}/#{id}-#{updated_at.to_s(:number)}"
2168:         else
2169:           "#{self.class.name.tableize}/#{id}"
2170:         end
2171:       end

Returns a clone of the record that hasn‘t been assigned an id yet and is treated as a new record. Note that this is a "shallow" clone: it copies the object‘s attributes only, not its associations. The extent of a "deep" clone is application-specific and is therefore left to the application to implement according to its need.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2228
2228:       def clone
2229:         attrs = clone_attributes(:read_attribute_before_type_cast)
2230:         attrs.delete(self.class.primary_key)
2231:         record = self.class.new
2232:         record.send :instance_variable_set, '@attributes', attrs
2233:         record
2234:       end

Returns the column object for the named attribute.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2416
2416:       def column_for_attribute(name)
2417:         self.class.columns_hash[name.to_s]
2418:       end

Returns the connection currently associated with the class. This can also be used to "borrow" the connection to do database work that isn‘t easily done without going straight to SQL.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 173
173:     def connection
174:       self.class.connection
175:     end

Initializes attribute to zero if nil and subtracts the value passed as by (default is 1). The decrement is performed directly on the underlying attribute, no setter is invoked. Only makes sense for number-based attributes. Returns self.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2292
2292:       def decrement(attribute, by = 1)
2293:         self[attribute] ||= 0
2294:         self[attribute] -= by
2295:         self
2296:       end

Wrapper around decrement that saves the record. This method differs from its non-bang version in that it passes through the attribute setter. Saving is not subjected to validation checks. Returns true if the record could be saved.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2302
2302:       def decrement!(attribute, by = 1)
2303:         decrement(attribute, by).update_attribute(attribute, self[attribute])
2304:       end

Deletes the record in the database and freezes this instance to reflect that no changes should be made (since they can‘t be persisted).

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2211
2211:       def destroy
2212:         unless new_record?
2213:           connection.delete "DELETE FROM \#{self.class.quoted_table_name}\nWHERE \#{connection.quote_column_name(self.class.primary_key)} = \#{quoted_id}\n", "#{self.class.name} Destroy"
2214:         end
2215: 
2216:         freeze
2217:       end

Delegates to ==

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2429
2429:       def eql?(comparison_object)
2430:         self == (comparison_object)
2431:       end

Freeze the attributes hash such that associations are still accessible, even on destroyed records.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2440
2440:       def freeze
2441:         @attributes.freeze; self
2442:       end

Returns true if the attributes hash has been frozen.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2445
2445:       def frozen?
2446:         @attributes.frozen?
2447:       end

Returns true if the given attribute is in the attributes hash

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2406
2406:       def has_attribute?(attr_name)
2407:         @attributes.has_key?(attr_name.to_s)
2408:       end

Delegates to id in order to allow two records of the same type and id to work with something like:

  [ Person.find(1), Person.find(2), Person.find(3) ] & [ Person.find(1), Person.find(4) ] # => [ Person.find(1) ]

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2435
2435:       def hash
2436:         id.hash
2437:       end

A model instance‘s primary key is always available as model.id whether you name it the default ‘id’ or set it to something else.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2139
2139:       def id
2140:         attr_name = self.class.primary_key
2141:         column = column_for_attribute(attr_name)
2142: 
2143:         self.class.send(:define_read_method, :id, attr_name, column)
2144:         # now that the method exists, call it
2145:         self.send attr_name.to_sym
2146: 
2147:       end

Sets the primary ID.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2182
2182:       def id=(value)
2183:         write_attribute(self.class.primary_key, value)
2184:       end

Initializes attribute to zero if nil and adds the value passed as by (default is 1). The increment is performed directly on the underlying attribute, no setter is invoked. Only makes sense for number-based attributes. Returns self.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2275
2275:       def increment(attribute, by = 1)
2276:         self[attribute] ||= 0
2277:         self[attribute] += by
2278:         self
2279:       end

Wrapper around increment that saves the record. This method differs from its non-bang version in that it passes through the attribute setter. Saving is not subjected to validation checks. Returns true if the record could be saved.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2285
2285:       def increment!(attribute, by = 1)
2286:         increment(attribute, by).update_attribute(attribute, self[attribute])
2287:       end

Returns the contents of the record as a nicely formatted string.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2461
2461:       def inspect
2462:         attributes_as_nice_string = self.class.column_names.collect { |name|
2463:           if has_attribute?(name) || new_record?
2464:             "#{name}: #{attribute_for_inspect(name)}"
2465:           end
2466:         }.compact.join(", ")
2467:         "#<#{self.class} #{attributes_as_nice_string}>"
2468:       end

Returns true if this object hasn‘t been saved yet — that is, a record for the object doesn‘t exist yet.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2187
2187:       def new_record?
2188:         defined?(@new_record) && @new_record
2189:       end

Marks this record as read only.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2456
2456:       def readonly!
2457:         @readonly = true
2458:       end

Returns true if the record is read only. Records loaded through joins with piggy-back attributes will be marked as read only since they cannot be saved.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2451
2451:       def readonly?
2452:         defined?(@readonly) && @readonly == true
2453:       end

Reloads the attributes of this object from the database. The optional options argument is passed to find when reloading so you may do e.g. record.reload(:lock => true) to reload the same record with an exclusive row lock.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2327
2327:       def reload(options = nil)
2328:         clear_aggregation_cache
2329:         clear_association_cache
2330:         @attributes.update(self.class.find(self.id, options).instance_variable_get('@attributes'))
2331:         @attributes_cache = {}
2332:         self
2333:       end
  • No record exists: Creates a new record with values matching those of the object attributes.
  • A record does exist: Updates the record with values matching those of the object attributes.

Note: If your model specifies any validations then the method declaration dynamically changes to:

  save(perform_validation=true)

Calling save(false) saves the model without running validations. See ActiveRecord::Validations for more information.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2199
2199:       def save
2200:         create_or_update
2201:       end

Attempts to save the record, but instead of just returning false if it couldn‘t happen, it raises a RecordNotSaved exception

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2205
2205:       def save!
2206:         create_or_update || raise(RecordNotSaved)
2207:       end

Enables Active Record objects to be used as URL parameters in Action Pack automatically.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2150
2150:       def to_param
2151:         # We can't use alias_method here, because method 'id' optimizes itself on the fly.
2152:         (id = self.id) ? id.to_s : nil # Be sure to stringify the id for routes
2153:       end

Assigns to attribute the boolean opposite of attribute?. So if the predicate returns true the attribute will become false. This method toggles directly the underlying value without calling any setter. Returns self.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2310
2310:       def toggle(attribute)
2311:         self[attribute] = !send("#{attribute}?")
2312:         self
2313:       end

Wrapper around toggle that saves the record. This method differs from its non-bang version in that it passes through the attribute setter. Saving is not subjected to validation checks. Returns true if the record could be saved.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2319
2319:       def toggle!(attribute)
2320:         toggle(attribute).update_attribute(attribute, self[attribute])
2321:       end

Updates a single attribute and saves the record. This is especially useful for boolean flags on existing records. Note: This method is overwritten by the Validation module that‘ll make sure that updates made with this method aren‘t subjected to validation checks. Hence, attributes can be updated even if the full object isn‘t valid.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2254
2254:       def update_attribute(name, value)
2255:         send(name.to_s + '=', value)
2256:         save
2257:       end

Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2261
2261:       def update_attributes(attributes)
2262:         self.attributes = attributes
2263:         save
2264:       end

Updates an object just like Base.update_attributes but calls save! instead of save so an exception is raised if the record is invalid.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 2267
2267:       def update_attributes!(attributes)
2268:         self.attributes = attributes
2269:         save!
2270:       end

[Validate]