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

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

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

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

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

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

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

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

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

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")

Use the find_or_initialize_by_ finder if you want to return a new record without saving it first. Example:

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

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
Constants
VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset, :order, :select, :readonly, :group, :from, :lock ]
Attributes
[RW] abstract_class Set this to true if this is an abstract class (see abstract_class?).
Public Class methods
===(object)

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 955
955:       def ===(object)
956:         object.is_a?(self)
957:       end
abstract_class?()

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 981
981:       def abstract_class?
982:         abstract_class == true
983:       end
attr_accessible(*attributes)

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 563
563:       def attr_accessible(*attributes)
564:         write_inheritable_array("attr_accessible", attributes - (accessible_attributes || []))
565:       end
attr_protected(*attributes)

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"
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 550
550:       def attr_protected(*attributes)
551:         write_inheritable_array("attr_protected", attributes - (protected_attributes || []))
552:       end
base_class()

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 972
972:       def base_class
973:         class_of_active_record_descendant(self)
974:       end
benchmark(title, log_level = Logger::DEBUG, use_silence = true) {|| ...}

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 850
850:       def benchmark(title, log_level = Logger::DEBUG, use_silence = true)
851:         if logger && logger.level == log_level
852:           result = nil
853:           seconds = Benchmark.realtime { result = use_silence ? silence { yield } : yield }
854:           logger.add(log_level, "#{title} (#{'%.5f' % seconds})")
855:           result
856:         else
857:           yield
858:         end
859:       end
clear_active_connections!()

Clears the cache which maps classes to connections.

    # 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
clear_reloadable_connections!()

Clears the cache which maps classes

    # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 91
91:       def clear_reloadable_connections!
92:         @@active_connections.each do |name, conn|
93:           if conn.requires_reloading?
94:             conn.disconnect!
95:             @@active_connections.delete(name)
96:           end
97:         end
98:       end
column_names()

Returns an array of column names as strings.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 772
772:       def column_names
773:         @column_names ||= columns.map { |column| column.name }
774:       end
columns()

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 758
758:       def columns
759:         unless @columns
760:           @columns = connection.columns(table_name, "#{name} Columns")
761:           @columns.each {|column| column.primary = column.name == primary_key}
762:         end
763:         @columns
764:       end
columns_hash()

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 767
767:       def columns_hash
768:         @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash }
769:       end
connected?()

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

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 239
239:     def self.connected?
240:       active_connections[active_connection_name] ? true : false
241:     end
connection()

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.

    # 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
connection=(spec)
    # 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
content_columns()

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 778
778:       def content_columns
779:         @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
780:       end
count_by_sql(sql)

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"
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 515
515:       def count_by_sql(sql)
516:         sql = sanitize_conditions(sql)
517:         connection.select_value(sql, "#{name} Count").to_i
518:       end
create(attributes = nil)

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 442
442:       def create(attributes = nil)
443:         if attributes.is_a?(Array)
444:           attributes.collect { |attr| create(attr) }
445:         else
446:           object = new(attributes)
447:           scope(:create).each { |att,value| object.send("#{att}=", value) } if scoped?(:create)
448:           object.save
449:           object
450:         end
451:       end
decrement_counter(counter_name, id)

Works like increment_counter, but decrements instead.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 530
530:       def decrement_counter(counter_name, id)
531:         update_all "#{counter_name} = #{counter_name} - 1", "#{primary_key} = #{quote_value(id)}"
532:       end
delete(id)

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 478
478:       def delete(id)
479:         delete_all([ "#{primary_key} IN (?)", id ])
480:       end
delete_all(conditions = nil)

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')"
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 507
507:       def delete_all(conditions = nil)
508:         sql = "DELETE FROM #{table_name} "
509:         add_conditions!(sql, conditions, scope(:find))
510:         connection.delete(sql, "#{name} Delete all")
511:       end
destroy(id)

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 484
484:       def destroy(id)
485:         id.is_a?(Array) ? id.each { |id| destroy(id) } : find(id).destroy
486:       end
destroy_all(conditions = nil)

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'"
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 500
500:       def destroy_all(conditions = nil)
501:         find(:all, :conditions => conditions).each { |object| object.destroy }
502:       end
establish_connection(spec = nil)

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.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 191
191:     def self.establish_connection(spec = nil)
192:       case spec
193:         when nil
194:           raise AdapterNotSpecified unless defined? RAILS_ENV
195:           establish_connection(RAILS_ENV)
196:         when ConnectionSpecification
197:           clear_active_connection_name
198:           @active_connection_name = name
199:           @@defined_connections[name] = spec
200:         when Symbol, String
201:           if configuration = configurations[spec.to_s]
202:             establish_connection(configuration)
203:           else
204:             raise AdapterNotSpecified, "#{spec} database is not configured"
205:           end
206:         else
207:           spec = spec.symbolize_keys
208:           unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end
209:           adapter_method = "#{spec[:adapter]}_connection"
210:           unless respond_to?(adapter_method) then raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter" end
211:           remove_connection
212:           establish_connection(ConnectionSpecification.new(spec, adapter_method))
213:       end
214:     end
exists?(id_or_conditions)

Returns true if the given id represents the primary key of a record in the database, false otherwise. You can also pass a set of SQL conditions. Example:

  Person.exists?(5)
  Person.exists?('5')
  Person.exists?(:name => "David")
  Person.exists?(['name LIKE ?', "%#{query}%"])
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 434
434:       def exists?(id_or_conditions)
435:         !find(:first, :conditions => expand_id_conditions(id_or_conditions)).nil?
436:       rescue ActiveRecord::ActiveRecordError
437:         false
438:       end
find(*args)

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.
  • :from: By default, this is the table name of the class, but can be changed to an alternate table name (or even the name of a database view).
  • :readonly: Mark the returned records read-only so they cannot be saved or updated.
  • :lock: An SQL fragment like "FOR UPDATE" or "LOCK IN SHARE MODE". :lock => true gives connection‘s default exclusive lock, usually "FOR UPDATE".

Examples 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")

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

  Person.transaction do
    person = Person.find(1, :lock => true)
    person.visits += 1
    person.save!
  end
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 408
408:       def find(*args)
409:         options = extract_options_from_args!(args)
410:         validate_find_options(options)
411:         set_readonly_option!(options)
412: 
413:         case args.first
414:           when :first then find_initial(options)
415:           when :all   then find_every(options)
416:           else             find_from_ids(args, options)
417:         end
418:       end
find_by_sql(sql)

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]
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 423
423:       def find_by_sql(sql)
424:         connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
425:       end
increment_counter(counter_name, id)

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 525
525:       def increment_counter(counter_name, id)
526:         update_all "#{counter_name} = #{counter_name} + 1", "#{primary_key} = #{quote_value(id)}"
527:       end
inheritance_column()

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 653
653:       def inheritance_column
654:         @inheritance_column ||= "type".freeze
655:       end
new(attributes = nil) {|self if block_given?| ...}

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1489
1489:       def initialize(attributes = nil)
1490:         @attributes = attributes_from_column_definition
1491:         @new_record = true
1492:         ensure_proper_type
1493:         self.attributes = attributes unless attributes.nil?
1494:         yield self if block_given?
1495:       end
primary_key()

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 635
635:       def primary_key
636:         reset_primary_key
637:       end
remove_connection(klass=self)

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.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 247
247:     def self.remove_connection(klass=self)
248:       spec = @@defined_connections[klass.name]
249:       konn = active_connections[klass.name]
250:       @@defined_connections.delete_if { |key, value| value == spec }
251:       active_connections.delete_if { |key, value| value == konn }
252:       konn.disconnect! if konn
253:       spec.config if spec
254:     end
require_mysql()
    # File vendor/rails/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb, line 46
46:     def self.require_mysql
47:       # Include the MySQL driver if one hasn't already been loaded
48:       unless defined? Mysql
49:         begin
50:           require_library_or_gem 'mysql'
51:         rescue LoadError => cannot_require_mysql
52:           # Use the bundled Ruby/MySQL driver if no driver is already in place
53:           begin
54:             require 'active_record/vendor/mysql'
55:           rescue LoadError
56:             raise cannot_require_mysql
57:           end
58:         end
59:       end
60: 
61:       # Define Mysql::Result.all_hashes
62:       MysqlCompat.define_all_hashes_method!
63:     end
reset_column_information()

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 802
802:       def reset_column_information
803:         read_methods.each { |name| undef_method(name) }
804:         @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @read_methods = @inheritance_column = nil
805:       end
serialize(attr_name, class_name = Object)

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.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 576
576:       def serialize(attr_name, class_name = Object)
577:         serialized_attributes[attr_name.to_s] = class_name
578:       end
serialized_attributes()

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

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 581
581:       def serialized_attributes
582:         read_inheritable_attribute("attr_serialized") or write_inheritable_attribute("attr_serialized", {})
583:       end
set_inheritance_column(value = nil, &block)

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
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 707
707:       def set_inheritance_column(value = nil, &block)
708:         define_attr_method :inheritance_column, value, &block
709:       end
set_primary_key(value = nil, &block)

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
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 691
691:       def set_primary_key(value = nil, &block)
692:         define_attr_method :primary_key, value, &block
693:       end
set_sequence_name(value = nil, &block)

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
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 728
728:       def set_sequence_name(value = nil, &block)
729:         define_attr_method :sequence_name, value, &block
730:       end
set_table_name(value = nil, &block)

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
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 677
677:       def set_table_name(value = nil, &block)
678:         define_attr_method :table_name, value, &block
679:       end
silence() {|| ...}

Silences the logger for the duration of the block.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 862
862:       def silence
863:         old_logger_level, logger.level = logger.level, Logger::ERROR if logger
864:         yield
865:       ensure
866:         logger.level = old_logger_level if logger
867:       end
table_exists?()

Indicates whether the table associated with this class exists

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 742
742:       def table_exists?
743:         if connection.respond_to?(:tables)
744:           connection.tables.include? table_name
745:         else
746:           # if the connection adapter hasn't implemented tables, there are two crude tests that can be
747:           # used - see if getting column info raises an error, or if the number of columns returned is zero
748:           begin
749:             reset_column_information
750:             columns.size > 0
751:           rescue ActiveRecord::StatementInvalid
752:             false
753:           end          
754:         end
755:       end
table_name()

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).

Nested classes are given table names prefixed by the singular form of the parent‘s table name. Example:

  file                  class               table_name
  invoice.rb            Invoice             invoices
  invoice/lineitem.rb   Invoice::Lineitem   invoice_lineitems

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

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

  class Mouse < ActiveRecord::Base
    set_table_name "mice"
  end
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 608
608:       def table_name
609:         reset_table_name
610:       end
update(id, attributes)

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)
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 465
465:       def update(id, attributes)
466:         if id.is_a?(Array)
467:           idx = -1
468:           id.collect { |id| idx += 1; update(id, attributes[idx]) }
469:         else
470:           object = find(id)
471:           object.update_attributes(attributes)
472:           object
473:         end
474:       end
update_all(updates, conditions = nil)

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'"
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 491
491:       def update_all(updates, conditions = nil)
492:         sql  = "UPDATE #{table_name} SET #{sanitize_sql(updates)} "
493:         add_conditions!(sql, conditions, scope(:find))
494:         connection.update(sql, "#{name} Update")
495:       end
with_exclusive_scope(method_scoping = {}, &block)

Works like with_scope, but discards any nested properties.

     # File vendor/rails/activerecord/lib/active_record/base.rb, line 950
950:       def with_exclusive_scope(method_scoping = {}, &block)
951:         with_scope(method_scoping, :overwrite, &block)
952:       end
with_scope(method_scoping = {}, action = :merge) {|| ...}

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
     # File vendor/rails/activerecord/lib/active_record/base.rb, line 898
898:       def with_scope(method_scoping = {}, action = :merge, &block)
899:         method_scoping = method_scoping.method_scoping if method_scoping.respond_to?(:method_scoping)
900: 
901:         # Dup first and second level of hash (method and params).
902:         method_scoping = method_scoping.inject({}) do |hash, (method, params)|
903:           hash[method] = (params == true) ? params : params.dup
904:           hash
905:         end
906: 
907:         method_scoping.assert_valid_keys([ :find, :create ])
908: 
909:         if f = method_scoping[:find]
910:           f.assert_valid_keys([ :conditions, :joins, :select, :include, :from, :offset, :limit, :order, :readonly, :lock ])
911:           f[:readonly] = true if !f[:joins].blank? && !f.has_key?(:readonly)
912:         end
913: 
914:         # Merge scopings
915:         if action == :merge && current_scoped_methods
916:           method_scoping = current_scoped_methods.inject(method_scoping) do |hash, (method, params)|
917:             case hash[method]
918:               when Hash
919:                 if method == :find
920:                   (hash[method].keys + params.keys).uniq.each do |key|
921:                     merge = hash[method][key] && params[key] # merge if both scopes have the same key
922:                     if key == :conditions && merge
923:                       hash[method][key] = [params[key], hash[method][key]].collect{ |sql| "( %s )" % sanitize_sql(sql) }.join(" AND ")
924:                     elsif key == :include && merge
925:                       hash[method][key] = merge_includes(hash[method][key], params[key]).uniq
926:                     else
927:                       hash[method][key] = hash[method][key] || params[key]
928:                     end
929:                   end
930:                 else
931:                   hash[method] = params.merge(hash[method])
932:                 end
933:               else
934:                 hash[method] = params
935:             end
936:             hash
937:           end
938:         end
939: 
940:         self.scoped_methods << method_scoping
941: 
942:         begin
943:           yield
944:         ensure
945:           self.scoped_methods.pop
946:         end
947:       end
Protected Class methods
class_of_active_record_descendant(klass)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1362
1362:         def class_of_active_record_descendant(klass)
1363:           if klass.superclass == Base || klass.superclass.abstract_class?
1364:             klass
1365:           elsif klass.superclass.nil?
1366:             raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
1367:           else
1368:             class_of_active_record_descendant(klass.superclass)
1369:           end
1370:         end
compute_type(type_name)

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1352
1352:         def compute_type(type_name)
1353:           modularized_name = type_name_with_module(type_name)
1354:           begin
1355:             class_eval(modularized_name, __FILE__, __LINE__)
1356:           rescue NameError
1357:             class_eval(type_name, __FILE__, __LINE__)
1358:           end
1359:         end
sanitize_sql(condition)

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

  ["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"
  { :name => "foo'bar", :group_id => 4 }  returns "name='foo''bar' and group_id='4'"
  "name='foo''bar' and group_id='4'" returns "name='foo''bar' and group_id='4'"
      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1382
1382:         def sanitize_sql(condition)
1383:           case condition
1384:             when Array; sanitize_sql_array(condition)
1385:             when Hash;  sanitize_sql_hash(condition)
1386:             else        condition
1387:           end
1388:         end
sanitize_sql_array(ary)

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

  ["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"
      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1406
1406:         def sanitize_sql_array(ary)
1407:           statement, *values = ary
1408:           if values.first.is_a?(Hash) and statement =~ /:\w+/
1409:             replace_named_bind_variables(statement, values.first)
1410:           elsif statement.include?('?')
1411:             replace_bind_variables(statement, values)
1412:           else
1413:             statement % values.collect { |value| connection.quote_string(value.to_s) }
1414:           end
1415:         end
sanitize_sql_hash(attrs)

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

  { :name => "foo'bar", :group_id => 4 }
    # => "name='foo''bar' and group_id= 4"
  { :status => nil, :group_id => [1,2,3] }
    # => "status IS NULL and group_id IN (1,2,3)"
      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1395
1395:         def sanitize_sql_hash(attrs)
1396:           conditions = attrs.map do |attr, value|
1397:             "#{table_name}.#{connection.quote_column_name(attr)} #{attribute_condition(value)}"
1398:           end.join(' AND ')
1399: 
1400:           replace_bind_variables(conditions, attrs.values)
1401:         end
Public Instance methods
==(comparison_object)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1717
1717:       def ==(comparison_object)
1718:         comparison_object.equal?(self) ||
1719:           (comparison_object.instance_of?(self.class) && 
1720:             comparison_object.id == id && 
1721:             !comparison_object.new_record?)
1722:       end
[](attr_name)

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).

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1639
1639:       def [](attr_name)
1640:         read_attribute(attr_name)
1641:       end
[]=(attr_name, value)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1645
1645:       def []=(attr_name, value)
1646:         write_attribute(attr_name, value)
1647:       end
attribute_names()

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1707
1707:       def attribute_names
1708:         @attributes.keys.sort
1709:       end
attribute_present?(attribute)

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).

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1696
1696:       def attribute_present?(attribute)
1697:         value = read_attribute(attribute)
1698:         !value.blank? or value == 0
1699:       end
attributes(options = nil)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1669
1669:       def attributes(options = nil)
1670:         attributes = clone_attributes :read_attribute
1671:         
1672:         if options.nil?
1673:           attributes
1674:         else
1675:           if except = options[:except]
1676:             except = Array(except).collect { |attribute| attribute.to_s }
1677:             except.each { |attribute_name| attributes.delete(attribute_name) }
1678:             attributes
1679:           elsif only = options[:only]
1680:             only = Array(only).collect { |attribute| attribute.to_s }
1681:             attributes.delete_if { |key, value| !only.include?(key) }
1682:             attributes
1683:           else
1684:             raise ArgumentError, "Options does not specify :except or :only (#{options.keys.inspect})"
1685:           end
1686:         end
1687:       end
attributes=(new_attributes)

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1654
1654:       def attributes=(new_attributes)
1655:         return if new_attributes.nil?
1656:         attributes = new_attributes.dup
1657:         attributes.stringify_keys!
1658: 
1659:         multi_parameter_attributes = []
1660:         remove_attributes_protected_from_mass_assignment(attributes).each do |k, v|
1661:           k.include?("(") ? multi_parameter_attributes << [ k, v ] : send(k + "=", v)
1662:         end
1663: 
1664:         assign_multiparameter_attributes(multi_parameter_attributes)
1665:       end
attributes_before_type_cast()

Returns a hash of cloned attributes before typecasting and deserialization.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1690
1690:       def attributes_before_type_cast
1691:         clone_attributes :read_attribute_before_type_cast
1692:       end
clone()

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1561
1561:       def clone
1562:         attrs = self.attributes_before_type_cast
1563:         attrs.delete(self.class.primary_key)
1564:         self.class.new do |record|
1565:           record.send :instance_variable_set, '@attributes', attrs
1566:         end
1567:       end
column_for_attribute(name)

Returns the column object for the named attribute.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1712
1712:       def column_for_attribute(name)
1713:         self.class.columns_hash[name.to_s]
1714:       end
connection()

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.

     # File vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 160
160:     def connection
161:       self.class.connection
162:     end
decrement(attribute)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1603
1603:       def decrement(attribute)
1604:         self[attribute] ||= 0
1605:         self[attribute] -= 1
1606:         self
1607:       end
decrement!(attribute)

Decrements the attribute and saves the record.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1610
1610:       def decrement!(attribute)
1611:         decrement(attribute).update_attribute(attribute, self[attribute])
1612:       end
destroy()

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1544
1544:       def destroy
1545:         unless new_record?
1546:           connection.delete "DELETE FROM \#{self.class.table_name}\nWHERE \#{self.class.primary_key} = \#{quoted_id}\n", "#{self.class.name} Destroy"
1547:         end
1548: 
1549:         freeze
1550:       end
eql?(comparison_object)

Delegates to ==

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1725
1725:       def eql?(comparison_object)
1726:         self == (comparison_object)
1727:       end
freeze()

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1757
1757:       def freeze
1758:         @attributes.freeze; self
1759:       end
frozen?()
      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1761
1761:       def frozen?
1762:         @attributes.frozen?
1763:       end
has_attribute?(attr_name)

Returns true if the given attribute is in the attributes hash

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1702
1702:       def has_attribute?(attr_name)
1703:         @attributes.has_key?(attr_name.to_s)
1704:       end
hash()

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) ]
      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1731
1731:       def hash
1732:         id.hash
1733:       end
id()

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1499
1499:       def id
1500:         attr_name = self.class.primary_key
1501:         column = column_for_attribute(attr_name)
1502:         define_read_method(:id, attr_name, column) if self.class.generate_read_methods
1503:         read_attribute(attr_name)
1504:       end
id=(value)

Sets the primary ID.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1521
1521:       def id=(value)
1522:         write_attribute(self.class.primary_key, value)
1523:       end
increment(attribute)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1591
1591:       def increment(attribute)
1592:         self[attribute] ||= 0
1593:         self[attribute] += 1
1594:         self
1595:       end
increment!(attribute)

Increments the attribute and saves the record.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1598
1598:       def increment!(attribute)
1599:         increment(attribute).update_attribute(attribute, self[attribute])
1600:       end
new_record?()

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1526
1526:       def new_record?
1527:         @new_record
1528:       end
readonly?()

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1766
1766:       def readonly?
1767:         @readonly == true
1768:       end
reload(options = nil)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1629
1629:       def reload(options = nil)
1630:         clear_aggregation_cache
1631:         clear_association_cache
1632:         @attributes.update(self.class.find(self.id, options).instance_variable_get('@attributes'))
1633:         self
1634:       end
respond_to?(method, include_priv = false)

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1740
1740:       def respond_to?(method, include_priv = false)
1741:         if @attributes.nil?
1742:           return super
1743:         elsif attr_name = self.class.column_methods_hash[method.to_sym]
1744:           return true if @attributes.include?(attr_name) || attr_name == self.class.primary_key
1745:           return false if self.class.read_methods.include?(attr_name)
1746:         elsif @attributes.include?(method_name = method.to_s)
1747:           return true
1748:         elsif md = self.class.match_attribute_method?(method.to_s)
1749:           return true if @attributes.include?(md.pre_match)
1750:         end
1751:         # super must be called at the end of the method, because the inherited respond_to?
1752:         # would return true for generated readers, even if the attribute wasn't present
1753:         super
1754:       end
save()
  • 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.
      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1532
1532:       def save
1533:         create_or_update
1534:       end
save!()

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1538
1538:       def save!
1539:         create_or_update || raise(RecordNotSaved)
1540:       end
to_param()

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1507
1507:       def to_param
1508:         # We can't use alias_method here, because method 'id' optimizes itself on the fly.
1509:         (id = self.id) ? id.to_s : nil # Be sure to stringify the id for routes
1510:       end
toggle(attribute)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1615
1615:       def toggle(attribute)
1616:         self[attribute] = !send("#{attribute}?")
1617:         self
1618:       end
toggle!(attribute)

Toggles the attribute and saves the record.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1621
1621:       def toggle!(attribute)
1622:         toggle(attribute).update_attribute(attribute, self[attribute])
1623:       end
update_attribute(name, value)

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1572
1572:       def update_attribute(name, value)
1573:         send(name.to_s + '=', value)
1574:         save
1575:       end
update_attributes(attributes)

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.

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1579
1579:       def update_attributes(attributes)
1580:         self.attributes = attributes
1581:         save
1582:       end
update_attributes!(attributes)

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

      # File vendor/rails/activerecord/lib/active_record/base.rb, line 1585
1585:       def update_attributes!(attributes)
1586:         self.attributes = attributes
1587:         save!
1588:       end