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/oracle_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/sqlserver_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/sybase_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/db2_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/openbase_adapter.rb
vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.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 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 don’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 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, 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").

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. 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")

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 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.
  • AdapterNotFound — 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

Reloadable::Subclasses

Constants

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

External Aliases

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

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 885
885:       def ===(object)
886:         object.is_a?(self)
887:       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 911
911:       def abstract_class?
912:         abstract_class == true
913:       end

If this macro is used, only those attributes 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 523
523:       def attr_accessible(*attributes)
524:         write_inheritable_array("attr_accessible", attributes - (accessible_attributes || []))
525:       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 from being 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 510
510:       def attr_protected(*attributes)
511:         write_inheritable_array("attr_protected", attributes - (protected_attributes || []))
512:       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 902
902:       def base_class
903:         class_of_active_record_descendant(self)
904:       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 matches 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 780
780:       def benchmark(title, log_level = Logger::DEBUG, use_silence = true)
781:         if logger && logger.level == log_level
782:           result = nil
783:           seconds = Benchmark.realtime { result = use_silence ? silence { yield } : yield }
784:           logger.add(log_level, "#{title} (#{'%.5f' % seconds})")
785:           result
786:         else
787:           yield
788:         end
789:       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

Returns an array of column names as strings.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 708
708:       def column_names
709:         @column_names ||= columns.map { |column| column.name }
710:       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 694
694:       def columns
695:         unless @columns
696:           @columns = connection.columns(table_name, "#{name} Columns")
697:           @columns.each {|column| column.primary = column.name == primary_key}
698:         end
699:         @columns
700:       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 703
703:       def columns_hash
704:         @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash }
705:       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/connection_specification.rb, line 229
229:     def self.connected?
230:       active_connections[active_connection_name] ? true : false
231:     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 @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

[Source]

    # File vendor/rails/activerecord/lib/active_record/query_cache.rb, line 50
50:       def connection=(spec)
51:         if spec.is_a?(ConnectionSpecification) and spec.config[:query_cache]
52:           spec = QueryCache.new(self.send(spec.adapter_method, spec.config))
53:         end
54:         self.connection_without_query_cache = spec
55:       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 714
714:       def content_columns
715:         @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
716:       end

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

  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 475
475:       def count_by_sql(sql)
476:         sql = sanitize_conditions(sql)
477:         connection.select_value(sql, "#{name} Count").to_i
478:       end

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 402
402:       def create(attributes = nil)
403:         if attributes.is_a?(Array)
404:           attributes.collect { |attr| create(attr) }
405:         else
406:           object = new(attributes)
407:           scope(:create).each { |att,value| object.send("#{att}=", value) } if scoped?(:create)
408:           object.save
409:           object
410:         end
411:       end

Works like increment_counter, but decrements instead.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 490
490:       def decrement_counter(counter_name, id)
491:         update_all "#{counter_name} = #{counter_name} - 1", "#{primary_key} = #{quote(id)}"
492:       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 438
438:       def delete(id)
439:         delete_all([ "#{primary_key} IN (?)", id ])
440:       end

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

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 467
467:       def delete_all(conditions = nil)
468:         sql = "DELETE FROM #{table_name} "
469:         add_conditions!(sql, conditions, scope(:find))
470:         connection.delete(sql, "#{name} Delete all")
471:       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 444
444:       def destroy(id)
445:         id.is_a?(Array) ? id.each { |id| destroy(id) } : find(id).destroy
446:       end

Destroys the objects for all the records that match 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 460
460:       def destroy_all(conditions = nil)
461:         find(:all, :conditions => conditions).each { |object| object.destroy }
462:       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 181
181:     def self.establish_connection(spec = nil)
182:       case spec
183:         when nil
184:           raise AdapterNotSpecified unless defined? RAILS_ENV
185:           establish_connection(RAILS_ENV)
186:         when ConnectionSpecification
187:           clear_active_connection_name
188:           @active_connection_name = name
189:           @@defined_connections[name] = spec
190:         when Symbol, String
191:           if configuration = configurations[spec.to_s]
192:             establish_connection(configuration)
193:           else
194:             raise AdapterNotSpecified, "#{spec} database is not configured"
195:           end
196:         else
197:           spec = spec.symbolize_keys
198:           unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
199:           adapter_method = "#{spec[:adapter]}_connection"
200:           unless respond_to?(adapter_method) then raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter" end
201:           remove_connection
202:           establish_connection(ConnectionSpecification.new(spec, adapter_method))
203:       end
204:     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 396
396:       def exists?(id)
397:         !find(:first, :conditions => ["#{primary_key} = ?", id]).nil? rescue false
398:       end

Find operates with three 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 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 accept 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".
  • :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 the first 4 rows.
  • :joins: An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed). 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 using LEFT OUTER JOINs. 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.
  • :readonly: Mark the returned records read-only so they cannot be saved or updated.

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 ])
  Person.find(:all, :group => "category")

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 374
374:       def find(*args)
375:         options = extract_options_from_args!(args)
376:         validate_find_options(options)
377:         set_readonly_option!(options)
378: 
379:         case args.first
380:           when :first then find_initial(options)
381:           when :all   then find_every(options)
382:           else             find_from_ids(args, options)
383:         end
384:       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 389
389:       def find_by_sql(sql)
390:         connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
391:       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 don’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 485
485:       def increment_counter(counter_name, id)
486:         update_all "#{counter_name} = #{counter_name} + 1", "#{primary_key} = #{quote(id)}"
487:       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 589
589:       def inheritance_column
590:         "type"
591:       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 1350
1350:       def initialize(attributes = nil)
1351:         @attributes = attributes_from_column_definition
1352:         @new_record = true
1353:         ensure_proper_type
1354:         self.attributes = attributes unless attributes.nil?
1355:         yield self if block_given?
1356:       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 572
572:       def primary_key
573:         reset_primary_key
574:       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/connection_specification.rb, line 237
237:     def self.remove_connection(klass=self)
238:       spec = @@defined_connections[klass.name]
239:       konn = active_connections[klass.name]
240:       @@defined_connections.delete_if { |key, value| value == spec }
241:       active_connections.delete_if { |key, value| value == konn }
242:       konn.disconnect! if konn
243:       spec.config if spec
244:     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 738
738:       def reset_column_information
739:         read_methods.each { |name| undef_method(name) }
740:         @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @read_methods = nil
741:       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 536
536:       def serialize(attr_name, class_name = Object)
537:         serialized_attributes[attr_name.to_s] = class_name
538:       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 541
541:       def serialized_attributes
542:         read_inheritable_attribute("attr_serialized") or write_inheritable_attribute("attr_serialized", {})
543:       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 643
643:       def set_inheritance_column(value = nil, &block)
644:         define_attr_method :inheritance_column, value, &block
645:       end

[Source]

    # File vendor/rails/activerecord/lib/active_record/locking.rb, line 64
64:       def set_locking_column(value = nil, &block)
65:         define_attr_method :locking_column, value, &block
66:       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 627
627:       def set_primary_key(value = nil, &block)
628:         define_attr_method :primary_key, value, &block
629:       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.

Example:

  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 664
664:       def set_sequence_name(value = nil, &block)
665:         define_attr_method :sequence_name, value, &block
666:       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 613
613:       def set_table_name(value = nil, &block)
614:         define_attr_method :table_name, value, &block
615:       end

Silences the logger for the duration of the block.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 792
792:       def silence
793:         old_logger_level, logger.level = logger.level, Logger::ERROR if logger
794:         yield
795:       ensure
796:         logger.level = old_logger_level if logger
797:       end

Indicates whether the table associated with this class exists

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 678
678:       def table_exists?
679:         if connection.respond_to?(:tables)
680:           connection.tables.include? table_name
681:         else
682:           # if the connection adapter hasn't implemented tables, there are two crude tests that can be
683:           # used - see if getting column info raises an error, or if the number of columns returned is zero
684:           begin
685:             reset_column_information
686:             columns.size > 0
687:           rescue ActiveRecord::StatementInvalid
688:             false
689:           end          
690:         end
691:       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 560
560:       def table_name
561:         reset_table_name
562:       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 fails under validations, the unsaved object is still returned.

The arguments may also be given as arrays in which case the update method is called for each pair of id and attributes and an array of objects is returned.

Example of updating one record:

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

Example of 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 425
425:       def update(id, attributes)
426:         if id.is_a?(Array)
427:           idx = -1
428:           id.collect { |id| idx += 1; update(id, attributes[idx]) }
429:         else
430:           object = find(id)
431:           object.update_attributes(attributes)
432:           object
433:         end
434:       end

Updates all records with the SET-part of an SQL update statement in updates and returns an integer with the number of rows updated. 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 451
451:       def update_all(updates, conditions = nil)
452:         sql  = "UPDATE #{table_name} SET #{sanitize_sql(updates)} "
453:         add_conditions!(sql, conditions, scope(:find))
454:         connection.update(sql, "#{name} Update")
455:       end

Works like with_scope, but discards any nested properties.

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 880
880:       def with_exclusive_scope(method_scoping = {}, &block)
881:         with_scope(method_scoping, :overwrite, &block)
882:       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.

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

In nested scopings, all previous parameters are overwritten by inner rule except :conditions in :find, that are merged as hash.

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

You can ignore any previous scopings by using with_exclusive_scope method.

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

[Source]

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 828
828:       def with_scope(method_scoping = {}, action = :merge, &block)
829:         method_scoping = method_scoping.method_scoping if method_scoping.respond_to?(:method_scoping)
830: 
831:         # Dup first and second level of hash (method and params).
832:         method_scoping = method_scoping.inject({}) do |hash, (method, params)|
833:           hash[method] = (params == true) ? params : params.dup
834:           hash
835:         end
836: 
837:         method_scoping.assert_valid_keys([ :find, :create ])
838: 
839:         if f = method_scoping[:find]
840:           f.assert_valid_keys([ :conditions, :joins, :select, :include, :from, :offset, :limit, :readonly ])
841:           f[:readonly] = true if !f[:joins].blank? && !f.has_key?(:readonly)
842:         end
843: 
844:         # Merge scopings
845:         if action == :merge && current_scoped_methods
846:           method_scoping = current_scoped_methods.inject(method_scoping) do |hash, (method, params)|
847:             case hash[method]
848:               when Hash
849:                 if method == :find
850:                   (hash[method].keys + params.keys).uniq.each do |key|
851:                     merge = hash[method][key] && params[key] # merge if both scopes have the same key
852:                     if key == :conditions && merge
853:                       hash[method][key] = [params[key], hash[method][key]].collect{ |sql| "( %s )" % sanitize_sql(sql) }.join(" AND ")
854:                     elsif key == :include && merge
855:                       hash[method][key] = merge_includes(hash[method][key], params[key]).uniq
856:                     else
857:                       hash[method][key] = hash[method][key] || params[key]
858:                     end
859:                   end
860:                 else
861:                   hash[method] = params.merge(hash[method])
862:                 end
863:               else
864:                 hash[method] = params
865:             end
866:             hash
867:           end
868:         end
869: 
870:         self.scoped_methods << method_scoping
871: 
872:         begin
873:           yield
874:         ensure
875:           self.scoped_methods.pop
876:         end
877:       end

Protected Class methods

Returns the class descending directly from ActiveRecord in the inheritance hierarchy.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1251
1251:         def class_of_active_record_descendant(klass)
1252:           if klass.superclass == Base || klass.superclass.abstract_class?
1253:             klass
1254:           elsif klass.superclass.nil?
1255:             raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
1256:           else
1257:             class_of_active_record_descendant(klass.superclass)
1258:           end
1259:         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 1241
1241:         def compute_type(type_name)
1242:           modularized_name = type_name_with_module(type_name)
1243:           begin
1244:             instance_eval(modularized_name)
1245:           rescue NameError => e
1246:             instance_eval(type_name)
1247:           end
1248:         end

Accepts an array or string. The string is returned untouched, but 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 1269
1269:         def sanitize_sql(ary)
1270:           return ary unless ary.is_a?(Array)
1271: 
1272:           statement, *values = ary
1273:           if values.first.is_a?(Hash) and statement =~ /:\w+/
1274:             replace_named_bind_variables(statement, values.first)
1275:           elsif statement.include?('?')
1276:             replace_bind_variables(statement, values)
1277:           else
1278:             statement % values.collect { |value| connection.quote_string(value.to_s) }
1279:           end
1280:         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 1567
1567:       def ==(comparison_object)
1568:         comparison_object.equal?(self) ||
1569:           (comparison_object.instance_of?(self.class) && 
1570:             comparison_object.id == id && 
1571:             !comparison_object.new_record?)
1572:       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 1489
1489:       def [](attr_name)
1490:         read_attribute(attr_name)
1491:       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 1495
1495:       def []=(attr_name, value)
1496:         write_attribute(attr_name, value)
1497:       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 1557
1557:       def attribute_names
1558:         @attributes.keys.sort
1559:       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 1546
1546:       def attribute_present?(attribute)
1547:         value = read_attribute(attribute)
1548:         !value.blank? or value == 0
1549:       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 1519
1519:       def attributes(options = nil)
1520:         attributes = clone_attributes :read_attribute
1521:         
1522:         if options.nil?
1523:           attributes
1524:         else
1525:           if except = options[:except]
1526:             except = Array(except).collect { |attribute| attribute.to_s }
1527:             except.each { |attribute_name| attributes.delete(attribute_name) }
1528:             attributes
1529:           elsif only = options[:only]
1530:             only = Array(only).collect { |attribute| attribute.to_s }
1531:             attributes.delete_if { |key, value| !only.include?(key) }
1532:             attributes
1533:           else
1534:             raise ArgumentError, "Options does not specify :except or :only (#{options.keys.inspect})"
1535:           end
1536:         end
1537:       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 1504
1504:       def attributes=(new_attributes)
1505:         return if new_attributes.nil?
1506:         attributes = new_attributes.dup
1507:         attributes.stringify_keys!
1508: 
1509:         multi_parameter_attributes = []
1510:         remove_attributes_protected_from_mass_assignment(attributes).each do |k, v|
1511:           k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v)
1512:         end
1513: 
1514:         assign_multiparameter_attributes(multi_parameter_attributes)
1515:       end

Returns a hash of cloned attributes before typecasting and deserialization.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1540
1540:       def attributes_before_type_cast
1541:         clone_attributes :read_attribute_before_type_cast
1542:       end
attributes_with_quotes_pre_oracle(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. 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 1420
1420:       def clone
1421:         attrs = self.attributes_before_type_cast
1422:         attrs.delete(self.class.primary_key)
1423:         self.class.new do |record|
1424:           record.send :instance_variable_set, '@attributes', attrs
1425:         end
1426:       end

Returns the column object for the named attribute.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1562
1562:       def column_for_attribute(name)
1563:         self.class.columns_hash[name.to_s]
1564:       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 150
150:     def connection
151:       self.class.connection
152:     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 1456
1456:       def decrement(attribute)
1457:         self[attribute] ||= 0
1458:         self[attribute] -= 1
1459:         self
1460:       end

Decrements the attribute and saves the record.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1463
1463:       def decrement!(attribute)
1464:         decrement(attribute).update_attribute(attribute, self[attribute])
1465:       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 1403
1403:       def destroy
1404:         unless new_record?
1405:           connection.delete "DELETE FROM \#{self.class.table_name}\nWHERE \#{self.class.primary_key} = \#{quoted_id}\n", "#{self.class.name} Destroy"
1406:         end
1407: 
1408:         freeze
1409:       end

Delegates to ==

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1575
1575:       def eql?(comparison_object)
1576:         self == (comparison_object)
1577:       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 1607
1607:       def freeze
1608:         @attributes.freeze; self
1609:       end

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1611
1611:       def frozen?
1612:         @attributes.frozen?
1613:       end

Returns true if the given attribute is in the attributes hash

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1552
1552:       def has_attribute?(attr_name)
1553:         @attributes.has_key?(attr_name.to_s)
1554:       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 1581
1581:       def hash
1582:         id.hash
1583:       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 1360
1360:       def id
1361:         attr_name = self.class.primary_key
1362:         column = column_for_attribute(attr_name)
1363:         define_read_method(:id, attr_name, column) if self.class.generate_read_methods
1364:         read_attribute(attr_name)
1365:       end

Sets the primary ID.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1379
1379:       def id=(value)
1380:         write_attribute(self.class.primary_key, value)
1381:       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 1444
1444:       def increment(attribute)
1445:         self[attribute] ||= 0
1446:         self[attribute] += 1
1447:         self
1448:       end

Increments the attribute and saves the record.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1451
1451:       def increment!(attribute)
1452:         increment(attribute).update_attribute(attribute, self[attribute])
1453:       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 1384
1384:       def new_record?
1385:         @new_record
1386:       end

Records loaded through joins with piggy-back attributes will be marked as read only as they cannot be saved and return true to this query.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1616
1616:       def readonly?
1617:         @readonly == true
1618:       end

Reloads the attributes of this object from the database.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1479
1479:       def reload
1480:         clear_aggregation_cache
1481:         clear_association_cache
1482:         @attributes.update(self.class.find(self.id).instance_variable_get('@attributes'))
1483:         self
1484:       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 1590
1590:       def respond_to?(method, include_priv = false)
1591:         if @attributes.nil?
1592:           return super 
1593:         elsif attr_name = self.class.column_methods_hash[method.to_sym]
1594:           return true if @attributes.include?(attr_name) || attr_name == self.class.primary_key
1595:           return false if self.class.read_methods.include?(attr_name)
1596:         elsif @attributes.include?(method_name = method.to_s)
1597:           return true
1598:         elsif md = /(=|\?|_before_type_cast)$/.match(method_name)
1599:           return true if @attributes.include?(md.pre_match)
1600:         end
1601:         # super must be called at the end of the method, because the inherited respond_to?
1602:         # would return true for generated readers, even if the attribute wasn't present
1603:         super
1604:       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 1390
1390:       def save
1391:         raise ReadOnlyRecord if readonly?
1392:         create_or_update
1393:       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 1397
1397:       def save!
1398:         save || raise(RecordNotSaved)
1399:       end
to_param()

Alias for id

Builds an XML document to represent the model. Some configuration is availble through options, however more complicated cases should use Builder.

By default the generated XML document will include the processing instruction and all object’s attributes. For example:

  <?xml version="1.0" encoding="UTF-8"?>
  <topic>
    <title>The First Topic</title>
    <author-name>David</author-name>
    <id type="integer">1</id>
    <approved type="boolean">false</approved>
    <replies-count type="integer">0</replies-count>
    <bonus-time type="datetime">2000-01-01T08:28:00+12:00</bonus-time>
    <written-on type="datetime">2003-07-16T09:28:00+1200</written-on>
    <content>Have a nice day</content>
    <author-email-address>david@loudthinking.com</author-email-address>
    <parent-id></parent-id>
    <last-read type="date">2004-04-15</last-read>
  </topic>

This behaviour can be controlled with :only, :except, and :skip_instruct for instance:

  topic.to_xml(:skip_instruct => true, :except => [ :id, bonus_time, :written_on, replies_count ])

  <topic>
    <title>The First Topic</title>
    <author-name>David</author-name>
    <approved type="boolean">false</approved>
    <content>Have a nice day</content>
    <author-email-address>david@loudthinking.com</author-email-address>
    <parent-id></parent-id>
    <last-read type="date">2004-04-15</last-read>
  </topic>

To include first level associations use :include

  firm.to_xml :include => [ :account, :clients ]

  <?xml version="1.0" encoding="UTF-8"?>
  <firm>
    <id type="integer">1</id>
    <rating type="integer">1</rating>
    <name>37signals</name>
    <clients>
      <client>
        <rating type="integer">1</rating>
        <name>Summit</name>
      </client>
      <client>
        <rating type="integer">1</rating>
        <name>Microsoft</name>
      </client>
    </clients>
    <account>
      <id type="integer">1</id>
      <credit-limit type="integer">50</credit-limit>
    </account>
  </firm>

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1685
1685:       def to_xml(options = {})
1686:         options[:root]    ||= self.class.to_s.underscore
1687:         options[:except]    = Array(options[:except]) << self.class.inheritance_column unless options[:only] # skip type column
1688:         root_only_or_except = { :only => options[:only], :except => options[:except] }
1689: 
1690:         attributes_for_xml = attributes(root_only_or_except)
1691:         
1692:         if include_associations = options.delete(:include)
1693:           include_has_options = include_associations.is_a?(Hash)
1694:           
1695:           for association in include_has_options ? include_associations.keys : Array(include_associations)
1696:             association_options = include_has_options ? include_associations[association] : root_only_or_except
1697: 
1698:             case self.class.reflect_on_association(association).macro
1699:               when :has_many, :has_and_belongs_to_many
1700:                 records = send(association).to_a
1701:                 unless records.empty?
1702:                   attributes_for_xml[association] = records.collect do |record| 
1703:                     record.attributes(association_options)
1704:                   end
1705:                 end
1706:               when :has_one, :belongs_to
1707:                 if record = send(association)
1708:                   attributes_for_xml[association] = record.attributes(association_options)
1709:                 end
1710:             end
1711:           end
1712:         end
1713: 
1714:         attributes_for_xml.to_xml(options)
1715:       end

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 1468
1468:       def toggle(attribute)
1469:         self[attribute] = !send("#{attribute}?")
1470:         self
1471:       end

Toggles the attribute and saves the record.

[Source]

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1474
1474:       def toggle!(attribute)
1475:         toggle(attribute).update_attribute(attribute, self[attribute])
1476:       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 1431
1431:       def update_attribute(name, value)
1432:         send(name.to_s + '=', value)
1433:         save
1434:       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 1438
1438:       def update_attributes(attributes)
1439:         self.attributes = attributes
1440:         save
1441:       end

[Validate]