Class ActiveRecord::Base
In: vendor/rails/activerecord/lib/active_record/locking.rb
vendor/rails/activerecord/lib/active_record/query_cache.rb
vendor/rails/activerecord/lib/active_record/timestamp.rb
vendor/rails/activerecord/lib/active_record/base.rb
vendor/rails/activerecord/lib/active_record/deprecated_finders.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/abstract_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/sqlserver_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/db2_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/oci_adapter.rb
Parent: Object

Active Record objects doesn’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 accepts 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 a 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 or an array 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 doesn’t involve tainted data. Examples:

  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
  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 a HTTP request. The authenticate_safely method, on the other hand, 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, [
    "id = :id AND name = :name AND division = :division AND created_at > :accounting_date",
    { :id => 3, :name => "37signals", :division => "First", :accounting_date => '2005-01-01' }
  ])

Overwriting default accessors

All column values are automatically available through basic accessors on the Active Record object, but some times you want to specialize this behavior. This can be done by either by overwriting the default accessors (using the same name as the attribute) 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 * 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, vaule) and read_attribute(:attribute) as a shorter form.

Accessing attributes before they have been type casted

Some times you want to be able to read the raw attribute data without having the column-determined type cast 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 type cast the string to 0, which isn’t what you want.

Dynamic attribute-based finders

Dynamic attribute-based finders are a cleaner way of getting 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, Payment.find_by_transaction_id. So instead of writing Person.find(:first, ["user_name = ?", user_name]), you just do Person.find_by_user_name(user_name). And instead of writing Person.find(:all, ["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, ["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").

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-mappeable 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 an 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 called "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 a ActiveRecord::Base, but resides in a different database you can just say Course.establish_connection and Course *and all 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

  • ActiveRecordError — generic error class and superclass of all other errors raised by Active Record
  • AdapterNotSpecified — the configuration hash used in establish_connection didn’t include a :adapter key.
  • AdapterNotSpecified — the :adapter key used in establish_connection specified an non-existent adapter (or a bad spelling of an existing one).
  • AssociationTypeMismatch — the object assigned to the association wasn’t of the type specified in the association definition.
  • SerializationTypeMismatch — the object serialized wasn’t of the class specified as the second parameter.
  • ConnectionNotEstablished — no connection has been established. Use establish_connection before querying.
  • RecordNotFound — no record responded to the find* method. Either the row with the given ID doesn’t exist or the row didn’t meet the additional restrictions.
  • StatementInvalid — the database server rejected the SQL statement. The precise error is added in the message. Either the record with the given ID doesn’t exist or the record didn’t meet the additional restrictions.
  • MultiparameterAssignmentErrors — collection of errors that occurred during a mass assignment using the +attributes=+ method. The errors property of this exception contains an array of AttributeAssignmentError objects that should be inspected to determine which attributes triggered the errors.
  • AttributeAssignmentError — an error occurred while doing a mass assignment through the +attributes=+ method. You can inspect the attribute property of the exception object to determine which attribute triggered the error.

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

Included Modules

ClassInheritableAttributes

External Aliases

set_table_name -> table_name=
set_primary_key -> primary_key=
set_inheritance_column -> inheritance_column=
sanitize_sql -> sanitize_conditions
respond_to? -> respond_to_without_attributes?
  For checking respond_to? without searching the attributes (which is faster).

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 714
714:       def ===(object)
715:         object.is_a?(self)
716:       end

If this macro is used, only those attributed named in it will be accessible for mass-assignment, such as new(attributes) and attributes=(attributes). This is the more conservative choice for mass-assignment protection. If you’d rather start from an all-open default and restrict attributes as needed, have a look at attr_protected.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 512
512:       def attr_accessible(*attributes)
513:         write_inheritable_array("attr_accessible", attributes)
514:       end

Attributes named in this macro are protected from mass-assignment, such as new(attributes) and attributes=(attributes). Their assignment will simply be ignored. Instead, you can use the direct writer methods to do assignment. This is meant to protect sensitive attributes to be overwritten by URL/form hackers. Example:

  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"

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 499
499:       def attr_protected(*attributes)
500:         write_inheritable_array("attr_protected", attributes)
501:       end

Log and benchmark multiple statements in a single block. Usage (hides all the SQL calls for the individual actions and calculates total runtime for them all):

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 698
698:       def benchmark(title)
699:         result = nil
700:         seconds = Benchmark.realtime { result = silence { yield } }
701:         logger.info "#{title} (#{sprintf("%f", seconds)})" if logger
702:         return result
703:       end

Returns a hash of all the methods added to query each of the columns in the table with the name of the method as the key and true as the value. This makes it possible to do O(1) lookups in respond_to? to check if a given method for attribute is available.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 651
651:       def column_methods_hash
652:         @dynamic_methods_hash ||= column_names.inject(Hash.new(false)) do |methods, attr|
653:           methods[attr.to_sym]       = true
654:           methods["#{attr}=".to_sym] = true
655:           methods["#{attr}?".to_sym] = true
656:           methods["#{attr}_before_type_cast".to_sym] = true
657:           methods
658:         end
659:       end

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 638
638:       def column_names
639:         @column_names ||= columns.map { |column| column.name }
640:       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 629
629:       def columns
630:         @columns ||= connection.columns(table_name, "#{name} Columns")
631:       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 634
634:       def columns_hash
635:         @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash }
636:       end

Returns true if a connection that’s accessible to this class have already been opened.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 117
117:     def self.connected?
118:       klass = self
119:       until klass == ActiveRecord::Base.superclass
120:         if active_connections[klass]
121:           return true
122:         else
123:           klass = klass.superclass
124:         end
125:       end
126:       return false
127:     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/base.rb, line 238
238:     def self.connection
239:       retrieve_connection
240:     end

Set the connection for the class.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 141
141:     def self.connection=(spec)
142:       raise ConnectionNotEstablished unless spec
143:       conn = self.send(spec.adapter_method, spec.config)
144:       active_connections[self] = conn
145:     end

Set the connection for the class with caching on

[Source]

    # File vendor/rails/activerecord/lib/active_record/query_cache.rb, line 47
47:     def self.connection=(spec)
48:       raise ConnectionNotEstablished unless spec
49: 
50:       conn = spec.config[:query_cache] ?
51:         QueryCache.new(self.send(spec.adapter_method, spec.config)) :
52:         self.send(spec.adapter_method, spec.config)
53:       
54:       active_connections[self] = conn
55:     end

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 644
644:       def content_columns
645:         @content_columns ||= columns.reject { |c| c.name == primary_key || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
646:       end

Returns the number of records that meets the conditions. Zero is returned if no records match. Example:

  Product.count "sales > 1"

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 450
450:       def count(conditions = nil, joins = nil)
451:         sql  = "SELECT COUNT(*) FROM #{table_name} "
452:         sql << " #{joins} " if joins
453:         add_conditions!(sql, conditions)
454:         count_by_sql(sql)
455:       end

Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part.

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 459
459:       def count_by_sql(sql)
460:         sql = sanitize_conditions(sql)
461:         rows = connection.select_one(sql, "#{name} Count")
462: 
463:         if !rows.nil? and count = rows.values.first
464:           count.to_i
465:         else
466:           0
467:         end
468:       end

Creates an object, instantly saves it as a record (if the validation permits it), and returns it. If the save fail under validations, the unsaved object is still returned.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 388
388:       def create(attributes = nil)
389:         if attributes.is_a?(Array)
390:           attributes.collect { |attr| create(attr) }
391:         else
392:           object = new(attributes)
393:           object.save
394:           object
395:         end
396:       end

Works like increment_counter, but decrements instead.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 480
480:       def decrement_counter(counter_name, id)
481:         update_all "#{counter_name} = #{counter_name} - 1", "#{primary_key} = #{quote(id)}"
482:       end

Deletes the record with the given id without instantiating an object first. If an array of ids is provided, all of them are deleted.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 413
413:       def delete(id)
414:         delete_all([ "#{primary_key} IN (?)", id ])
415:       end

Deletes all the records that matches the condition without instantiating the objects first (and hence not calling the destroy method). Example:

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 442
442:       def delete_all(conditions = nil)
443:         sql = "DELETE FROM #{table_name} "
444:         add_conditions!(sql, conditions)
445:         connection.delete(sql, "#{name} Delete all")
446:       end

Destroys the record with the given id by instantiating the object and calling destroy (all the callbacks are the triggered). If an array of ids is provided, all of them are destroyed.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 419
419:       def destroy(id)
420:         id.is_a?(Array) ? id.each { |id| destroy(id) } : find(id).destroy
421:       end

Destroys the objects for all the records that matches the condition by instantiating each object and calling the destroy method. Example:

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 435
435:       def destroy_all(conditions = nil)
436:         find(:all, :conditions => conditions).each { |object| object.destroy }
437:       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",
    :dbfile  => "path/to/dbfile"
  )

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

  ActiveRecord::Base.establish_connection(
    "adapter" => "sqlite",
    "dbfile"  => "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_adapter.rb, line 66
66:     def self.establish_connection(spec = nil)
67:       case spec
68:         when nil
69:           raise AdapterNotSpecified unless defined? RAILS_ENV
70:           establish_connection(RAILS_ENV)
71:         when ConnectionSpecification
72:           @@defined_connections[self] = spec
73:         when Symbol, String
74:           if configuration = configurations[spec.to_s]
75:             establish_connection(configuration)
76:           else
77:             raise AdapterNotSpecified, "#{spec} database is not configured"
78:           end
79:         else
80:           spec = spec.symbolize_keys
81:           unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
82:           adapter_method = "#{spec[:adapter]}_connection"
83:           unless respond_to?(adapter_method) then raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter" end
84:           remove_connection
85:           establish_connection(ConnectionSpecification.new(spec, adapter_method))
86:       end
87:     end

Returns true if the given id represents the primary key of a record in the database, false otherwise. Example:

  Person.exists?(5)

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 382
382:       def exists?(id)
383:         !find(:first, :conditions => ["#{primary_key} = ?", id]).nil? rescue false
384:       end

Find operates with three different retreval 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 matched, nil is returned.
  • Find all: This will return all the records matched by the options used. If no records are found, an empty array is returned.

All approaches accepts an option hash as their last parameter. The options are:

  • :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".
  • :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 the first 4 rows.
  • :joins: An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed).
  • :include: Names associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer to already defined associations. See eager loading under Associations.

Examples for 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 objects the object with ID = 1
  Person.find(1, :conditions => "administrator = 1", :order => "created_on DESC")

Examples for 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)

Examples for 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, :offset => 10, :limit => 10)
  Person.find(:all, :include => [ :account, :friends ])

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 336
336:       def find(*args)
337:         options = extract_options_from_args!(args)
338: 
339:         case args.first
340:           when :first
341:             find(:all, options.merge(options[:include] ? { } : { :limit => 1 })).first
342:           when :all
343:             options[:include] ? find_with_associations(options) : find_by_sql(construct_finder_sql(options))
344:           else
345:             return args.first if args.first.kind_of?(Array) && args.first.empty?
346:             expects_array = args.first.kind_of?(Array)
347:             conditions = " AND #{sanitize_sql(options[:conditions])}" if options[:conditions]
348: 
349:             ids = args.flatten.compact.uniq
350:             case ids.size
351:               when 0
352:                 raise RecordNotFound, "Couldn't find #{name} without an ID#{conditions}"
353:               when 1
354:                 if result = find(:first, options.merge({ :conditions => "#{table_name}.#{primary_key} = #{sanitize(ids.first)}#{conditions}" }))
355:                   return expects_array ? [ result ] : result
356:                 else
357:                   raise RecordNotFound, "Couldn't find #{name} with ID=#{ids.first}#{conditions}"
358:                 end
359:               else
360:                 # Find multiple ids
361:                 ids_list = ids.map { |id| sanitize(id) }.join(',')
362:                 result   = find(:all, options.merge({ :conditions => "#{table_name}.#{primary_key} IN (#{ids_list})#{conditions}"}))
363:                 if result.size == ids.size
364:                   return result
365:                 else
366:                   raise RecordNotFound, "Couldn't find all #{name.pluralize} with IDs (#{ids_list})#{conditions}"
367:                 end
368:             end
369:         end
370:       end

Works like find(:all), but requires a complete SQL string. Examples:

  Post.find_by_sql "SELECT p.*, c.author FROM posts p, comments c WHERE p.id = c.post_id"
  Post.find_by_sql ["SELECT * FROM posts WHERE author = ? AND created > ?", author_id, start_date]

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 375
375:       def find_by_sql(sql)
376:         connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
377:       end

Increments the specified counter by one. So DiscussionBoard.increment_counter("post_count", discussion_board_id) would increment the "post_count" counter on the board responding to discussion_board_id. This is used for caching aggregate values, so that they doesn’t need to be computed every time. Especially important for looping over a collection where each element require a number of aggregate values. Like the DiscussionBoard that needs to list both the number of posts and comments.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 475
475:       def increment_counter(counter_name, id)
476:         update_all "#{counter_name} = #{counter_name} + 1", "#{primary_key} = #{quote(id)}"
477:       end

Defines the column name for use with single table inheritance — can be overridden in subclasses.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 570
570:       def inheritance_column
571:         "type"
572:       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 935
935:       def initialize(attributes = nil)
936:         @attributes = attributes_from_column_definition
937:         @new_record = true
938:         ensure_proper_type
939:         self.attributes = attributes unless attributes.nil?
940:         yield self if block_given?
941:       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 558
558:       def primary_key
559:         case primary_key_prefix_type
560:           when :table_name
561:             Inflector.foreign_key(class_name_of_active_record_descendant(self), false)
562:           when :table_name_with_underscore
563:             Inflector.foreign_key(class_name_of_active_record_descendant(self))
564:           else
565:             "id"
566:         end
567:       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 argument for establish_connection, for easy re-establishing of the connection.

[Source]

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb, line 133
133:     def self.remove_connection(klass=self)
134:       conn = @@defined_connections[klass]
135:       @@defined_connections.delete(klass)
136:       active_connections[klass] = nil
137:       conn.config if conn
138:     end

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 662
662:       def reset_column_information
663:         @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = nil
664:       end

Specifies that the attribute by the name of attr_name should be serialized before saving to the database and unserialized after loading from the database. 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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 524
524:       def serialize(attr_name, class_name = Object)
525:         serialized_attributes[attr_name.to_s] = class_name
526:       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 529
529:       def serialized_attributes
530:         read_inheritable_attribute("attr_serialized") or write_inheritable_attribute("attr_serialized", {})
531:       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.

Example:

  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 613
613:       def set_inheritance_column( value=nil, &block )
614:         define_attr_method :inheritance_column, value, &block
615:       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.

Example:

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 597
597:       def set_primary_key( value=nil, &block )
598:         define_attr_method :primary_key, value, &block
599:       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.

Example:

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 582
582:       def set_table_name( value=nil, &block )
583:         Inflector.add_table_class_relationships( name => value ) if Inflector.tableize( name ) != value
584:         define_attr_method :table_name, value, &block
585:       end

Silences the logger for the duration of the block.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 706
706:       def silence
707:         old_logger_level, logger.level = logger.level, Logger::ERROR if logger
708:         yield
709:       ensure
710:         logger.level = old_logger_level if logger
711:       end

Guesses the table name (in forced lower-case) based on the name of the class in the inheritance hierarchy descending directly from ActiveRecord. So if the hierarchy looks like: Reply < Message < ActiveRecord, then Message is used to guess the table name from 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 (report a bug if your inflection isn’t covered).

Additionally, the class-level table_name_prefix is prepended to the table_name and the table_name_suffix is appended. So if you have "myapp_" as a prefix, the table name guess for an Account class becomes "myapp_accounts".

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 547
547:       def table_name
548:         class_name = class_name_of_active_record_descendant(self)
549:         if Inflector.class_table_relationship?(class_name)
550:           Inflector.tableize(class_name)
551:         else
552:           "#{table_name_prefix}#{undecorated_table_name(class_name)}#{table_name_suffix}"
553:         end
554:       end

Finds the record from the passed id, instantly saves it with the passed attributes (if the validation permits it), and returns it. If the save fail under validations, the unsaved object is still returned.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 400
400:       def update(id, attributes)
401:         if id.is_a?(Array)
402:           idx = -1
403:           id.collect { |id| idx += 1; update(id, attributes[idx]) }
404:         else
405:           object = find(id)
406:           object.update_attributes(attributes)
407:           object
408:         end
409:       end

Updates all records with the SET-part of an SQL update statement in updates and returns an integer with the number of rows updates. A subset of the records can be selected by specifying conditions. Example:

  Billing.update_all "category = 'authorized', approved = 1", "author = 'David'"

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 426
426:       def update_all(updates, conditions = nil)
427:         sql  = "UPDATE #{table_name} SET #{sanitize_sql(updates)} "
428:         add_conditions!(sql, conditions)
429:         connection.update(sql, "#{name} Update")
430:       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 1113
1113:       def ==(comparison_object)
1114:         comparison_object.equal?(self) or (comparison_object.instance_of?(self.class) and comparison_object.id == id)
1115:       end

Returns the value of attribute identified by attr_name after it has been type cast (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 1059
1059:       def [](attr_name)
1060:         read_attribute(attr_name.to_s)
1061:       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 1065
1065:       def []=(attr_name, value)
1066:         write_attribute(attr_name.to_s, value)
1067:       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 1103
1103:       def attribute_names
1104:         @attributes.keys.sort
1105:       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 responds to empty?, most notably Strings).

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1097
1097:       def attribute_present?(attribute)
1098:         value = read_attribute(attribute)
1099:         !value.blank? or value == 0
1100:       end

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

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1086
1086:       def attributes
1087:         clone_attributes :read_attribute
1088:       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 in 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 1074
1074:       def attributes=(attributes)
1075:         return if attributes.nil?
1076:         attributes.stringify_keys!
1077: 
1078:         multi_parameter_attributes = []
1079:         remove_attributes_protected_from_mass_assignment(attributes).each do |k, v|
1080:           k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v)
1081:         end
1082:         assign_multiparameter_attributes(multi_parameter_attributes)
1083:       end

Returns a hash of cloned attributes before typecasting and deserialization.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1091
1091:       def attributes_before_type_cast
1092:         clone_attributes :read_attribute_before_type_cast
1093:       end
attributes_with_quotes_pre_oci(include_primary_key = true)

Alias for attributes_with_quotes

Returns a clone of the record that hasn’t been assigned an id yet and is treated as a new record.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 991
991:       def clone
992:         attrs = self.attributes_before_type_cast
993:         attrs.delete(self.class.primary_key)
994:         self.class.new do |record|
995:           record.send :instance_variable_set, '@attributes', attrs
996:         end
997:       end

Returns the column object for the named attribute.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1108
1108:       def column_for_attribute(name)
1109:         self.class.columns_hash[name.to_s]
1110:       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/base.rb, line 245
245:     def connection
246:       self.class.connection
247:     end

Initializes the attribute to zero if nil and subtracts one. Only makes sense for number-based attributes. Returns self.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1027
1027:       def decrement(attribute)
1028:         self[attribute] ||= 0
1029:         self[attribute] -= 1
1030:         self
1031:       end

Decrements the attribute and saves the record.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1034
1034:       def decrement!(attribute)
1035:         decrement(attribute).update_attribute(attribute, self[attribute])
1036:       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 978
978:       def destroy
979:         unless new_record?
980:           connection.delete "DELETE FROM \#{self.class.table_name}\nWHERE \#{self.class.primary_key} = \#{quoted_id}\n", "#{self.class.name} Destroy"
981:         end
982: 
983:         freeze
984:       end

Delegates to ==

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1118
1118:       def eql?(comparison_object)
1119:         self == (comparison_object)
1120:       end

Just 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 1138
1138:       def freeze
1139:         @attributes.freeze
1140:       end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1142
1142:       def frozen?
1143:         @attributes.frozen?
1144:       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 1124
1124:       def hash
1125:         id.hash
1126:       end

Every Active Record class must use "id" as their primary ID. This getter overwrites the native id method, which isn’t being used in this context.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 945
945:       def id
946:         read_attribute(self.class.primary_key)
947:       end

Sets the primary ID.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 961
961:       def id=(value)
962:         write_attribute(self.class.primary_key, value)
963:       end

Initializes the attribute to zero if nil and adds one. Only makes sense for number-based attributes. Returns self.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1015
1015:       def increment(attribute)
1016:         self[attribute] ||= 0
1017:         self[attribute] += 1
1018:         self
1019:       end

Increments the attribute and saves the record.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1022
1022:       def increment!(attribute)
1023:         increment(attribute).update_attribute(attribute, self[attribute])
1024:       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 966
966:       def new_record?
967:         @new_record
968:       end

Reloads the attributes of this object from the database.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1050
1050:       def reload
1051:         clear_association_cache
1052:         @attributes.update(self.class.find(self.id).instance_variable_get('@attributes'))
1053:         self
1054:       end

A Person object with a name attribute can ask person.respond_to?("name"), person.respond_to?("name="), and person.respond_to?("name?") which will all return true.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1133
1133:       def respond_to?(method, include_priv = false)
1134:         self.class.column_methods_hash[method.to_sym] || respond_to_without_attributes?(method, include_priv)
1135:       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.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 972
972:       def save
973:         create_or_update
974:       end
to_param()

Alias for id

Turns an attribute that’s currently true into false and vice versa. Returns self.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1039
1039:       def toggle(attribute)
1040:         self[attribute] = quote(!send("#{attribute}?", column_for_attribute(attribute)))
1041:         self
1042:       end

Toggles the attribute and saves the record.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1045
1045:       def toggle!(attribute)
1046:         toggle(attribute).update_attribute(attribute, self[attribute])
1047:       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 doesn’t get 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 1002
1002:       def update_attribute(name, value)
1003:         self[name] = value
1004:         save
1005:       end

Updates all the attributes in from the passed 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 1009
1009:       def update_attributes(attributes)
1010:         self.attributes = attributes
1011:         save
1012:       end

[Validate]