Active Record

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/activerecord/README_rdoc.html for more insight.

Creation

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

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

You can also use block initialization:

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

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

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

Conditions

Conditions can either be specified as a string, array, or hash representing the WHERE-part of an SQL statement. The array form is to be used when the condition input is tainted and requires sanitization. The string form can be used for statements that don’t involve tainted data. The hash form works much like the array form, except only equality and range is possible. Examples:

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

  def self.authenticate_safely(user_name, password)
    where("user_name = ? AND password = ?", user_name, password).first
  end

  def self.authenticate_safely_simply(user_name, password)
    where(:user_name => user_name, :password => password).first
  end
end

The authenticate_unsafely method inserts the parameters directly into the query and is thus susceptible to SQL-injection attacks if the user_name and password parameters come directly from an HTTP request. The authenticate_safely and authenticate_safely_simply both will sanitize the user_name and password before inserting them in the query, which will ensure that an attacker can’t escape the query and fake the login (or worse).

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

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

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

Student.where(:first_name => "Harvey", :status => 1)
Student.where(params[:student])

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

Student.where(:grade => 9..12)

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

Student.where(:grade => [9,11,12])

When joining tables, nested hashes or keys written in the form ‘table_name.column_name’ can be used to qualify the table name of a particular condition. For instance:

Student.joins(:schools).where(:schools => { :type => 'public' })
Student.joins(:schools).where('schools.type' => 'public' )

Overwriting default accessors

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

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

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

  def length
    read_attribute(:length) / 60
  end
end

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

Attribute query methods

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

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

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

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

Accessing attributes before they have been typecasted

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

This is especially useful in validation situations where the user might supply a string for an integer field and you want to display the original string back in an error message. Accessing the attribute normally would typecast the string to 0, which isn’t what you want.

Dynamic attribute-based finders

Dynamic attribute-based finders are a cleaner way of getting (and/or creating) objects by simple queries without turning to SQL. They work by appending the name of an attribute to find_by_, find_last_by_, or find_all_by_ and thus produces finders like Person.find_by_user_name, Person.find_all_by_last_name, and Payment.find_by_transaction_id. Instead of writing Person.where(:user_name => user_name).first, you just do Person.find_by_user_name(user_name). And instead of writing Person.where(:last_name => last_name).all, 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”.

Person.where(:user_name => user_name, :password => password).first
Person.find_by_user_name_and_password #with dynamic finder

Person.where(:user_name => user_name, :password => password, :gender => 'male').first
Payment.find_by_user_name_and_password_and_gender

It’s even possible to call these dynamic finder methods on relations and named scopes.

Payment.order("created_on").find_all_by_amount(50)
Payment.pending.find_last_by_amount(100)

The same dynamic finder style can be used to create the object if it doesn’t already exist. This dynamic finder is called with find_or_create_by_ and will return the object if it already exists and otherwise creates it, then returns it. Protected attributes won’t be set unless they are given in a block.

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

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

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

Use the find_or_initialize_by_ finder if you want to return a new record without saving it first. Protected attributes won’t be set unless they are given in a block.

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

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

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

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

Just like find_by_*, you can also use scoped_by_* to retrieve data. The good thing about using this feature is that the very first time result is returned using method_missing technique but after that the method is declared on the class. Henceforth method_missing will not be hit.

User.scoped_by_user_name('David')

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.

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 descendant of a class not in the hierarchy.

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

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

Single table inheritance

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

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

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

If you don’t have a type column defined in your table, single-table inheritance won’t be triggered. In that case, it’ll work just like normal subclasses with no special magic for differentiating between them or reloading the right type with find.

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

Connection to multiple databases in different models

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

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

Exceptions

  • 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 an :adapter key.

  • AdapterNotFound - The :adapter key used in establish_connection specified a 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 serialized object 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. Some find calls do not raise this exception to signal nothing was found, please check its documentation for further details.

  • StatementInvalid - The database server rejected the SQL statement. The precise error is added in the message.

  • 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
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 activerecord/lib/active_record/base.rb, line 819
def ===(object)
  object.is_a?(self)
end
abstract_class?()

Returns whether this class is an abstract class or not.

  # File activerecord/lib/active_record/base.rb, line 837
def abstract_class?
  defined?(@abstract_class) && @abstract_class == true
end
arel_engine()
  # File activerecord/lib/active_record/base.rb, line 859
def arel_engine
  @arel_engine ||= begin
    if self == ActiveRecord::Base
      Arel::Table.engine
    else
      connection_handler.connection_pools[name] ? self : superclass.arel_engine
    end
  end
end
arel_table()
  # File activerecord/lib/active_record/base.rb, line 855
def arel_table
  @arel_table ||= Arel::Table.new(table_name, arel_engine)
end
attr_readonly(*attributes)

Attributes listed as readonly will be used to create a new record but update operations will ignore these fields.

  # File activerecord/lib/active_record/base.rb, line 527
def attr_readonly(*attributes)
  write_inheritable_attribute(:attr_readonly, Set.new(attributes.map { |a| a.to_s }) + (readonly_attributes || []))
end
attribute_method?(attribute)
  # File activerecord/lib/active_record/base.rb, line 757
def attribute_method?(attribute)
  super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, '')))
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.

If B < A and C < B and if A is an abstract_class then both B.base_class and C.base_class would return B as the answer since A is an abstract_class.

  # File activerecord/lib/active_record/base.rb, line 829
def base_class
  class_of_active_record_descendant(self)
end
colorize_logging(*args)
This method is also aliased as colorize_logging=
  # File activerecord/lib/active_record/base.rb, line 437
def colorize_logging(*args)
  ActiveSupport::Deprecation.warn "ActiveRecord::Base.colorize_logging and " <<
    "config.active_record.colorize_logging are deprecated. Please use " <<
    "Rails::LogSubscriber.colorize_logging or config.colorize_logging instead", caller
end
column_names()

Returns an array of column names as strings.

  # File activerecord/lib/active_record/base.rb, line 697
def column_names
  @column_names ||= columns.map { |column| column.name }
end
columns()

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

  # File activerecord/lib/active_record/base.rb, line 683
def columns
  unless defined?(@columns) && @columns
    @columns = connection.columns(table_name, "#{name} Columns")
    @columns.each { |column| column.primary = column.name == primary_key }
  end
  @columns
end
columns_hash()

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

  # File activerecord/lib/active_record/base.rb, line 692
def columns_hash
  @columns_hash ||= Hash[columns.map { |column| [column.name, column] }]
end
configurations

Contains the database configuration - as is typically stored in config/database.yml - as a Hash.

For example, the following database.yml…

development:
  adapter: sqlite3
  database: db/development.sqlite3

production:
  adapter: sqlite3
  database: db/production.sqlite3

…would result in ActiveRecord::Base.configurations to look like this:

{
   'development' => {
      'adapter'  => 'sqlite3',
      'database' => 'db/development.sqlite3'
   },
   'production' => {
      'adapter'  => 'sqlite3',
      'database' => 'db/production.sqlite3'
   }
}
  # File activerecord/lib/active_record/base.rb, line 363
cattr_accessor :configurations, :instance_writer => false
connected?()

Returns true if Active Record is connected.

  # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 101
def connected?
  connection_handler.connected?(self)
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 activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 88
def connection
  retrieve_connection
end
connection_handler

The connection handler

  # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 13
class_attribute :connection_handler, :instance_writer => false
connection_pool()
  # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 92
def connection_pool
  connection_handler.retrieve_connection_pool(self)
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 activerecord/lib/active_record/base.rb, line 703
def content_columns
  @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
end
count_by_sql(sql)

Returns the result of an SQL statement that should only include a COUNT(*) in the SELECT part. The use of this method should be restricted to complicated SQL queries that can’t be executed using the ActiveRecord::Calculations class methods. Look into those before using this.

Parameters

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

Examples

Product.count_by_sql "SELECT COUNT(*) FROM sales s, customers c WHERE s.customer_id = c.id"
  # File activerecord/lib/active_record/base.rb, line 520
def count_by_sql(sql)
  sql = sanitize_conditions(sql)
  connection.select_value(sql, "#{name} Count").to_i
end
create(attributes = nil, &block)

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

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

Examples

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

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

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

# Creating an Array of new objects using a block, where the block is executed for each object:
User.create([{ :first_name => 'Jamie' }, { :first_name => 'Jeremy' }]) do |u|
  u.is_admin = false
end
  # File activerecord/lib/active_record/base.rb, line 498
def create(attributes = nil, &block)
  if attributes.is_a?(Array)
    attributes.collect { |attr| create(attr, &block) }
  else
    object = new(attributes)
    yield(object) if block_given?
    object.save
    object
  end
end
default_timezone

Determines whether to use Time.local (using :local) or Time.utc (using :utc) when pulling dates and times from the database. This is set to :local by default.

  # File activerecord/lib/active_record/base.rb, line 408
cattr_accessor :default_timezone, :instance_writer => false
descends_from_active_record?()

True if this isn’t a concrete subclass needing a STI type condition.

  # File activerecord/lib/active_record/base.rb, line 782
def descends_from_active_record?
  if superclass.abstract_class?
    superclass.descends_from_active_record?
  else
    superclass == Base || !columns_hash.include?(inheritance_column)
  end
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 activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 51
def self.establish_connection(spec = nil)
  case spec
    when nil
      raise AdapterNotSpecified unless defined?(Rails.env)
      establish_connection(Rails.env)
    when ConnectionSpecification
      self.connection_handler.establish_connection(name, spec)
    when Symbol, String
      if configuration = configurations[spec.to_s]
        establish_connection(configuration)
      else
        raise AdapterNotSpecified, "#{spec} database is not configured"
      end
    else
      spec = spec.symbolize_keys
      unless spec.key?(:adapter) then raise AdapterNotSpecified, "database configuration does not specify adapter" end

      begin
        require "active_record/connection_adapters/#{spec[:adapter]}_adapter"
      rescue LoadError => e
        raise "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{e})"
      end

      adapter_method = "#{spec[:adapter]}_connection"
      if !respond_to?(adapter_method)
        raise AdapterNotFound, "database configuration specifies nonexistent #{spec[:adapter]} adapter"
      end

      remove_connection
      establish_connection(ConnectionSpecification.new(spec, adapter_method))
  end
end
find_by_sql(sql)

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

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

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

Examples

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

# You can use the same string replacement techniques as you can with ActiveRecord#find
Post.find_by_sql ["SELECT title FROM posts WHERE author = ? AND created > ?", author_id, start_date]
> [#<Post:0x36bff9c @attributes={"first_name"=>"The Cheap Man Buys Twice"}>, ...]
  # File activerecord/lib/active_record/base.rb, line 472
def find_by_sql(sql)
  connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
end
inheritance_column()

Defines the column name for use with single table inheritance. Use set_inheritance_column to set a different value.

  # File activerecord/lib/active_record/base.rb, line 616
def inheritance_column
  @inheritance_column ||= "type"
end
inspect()

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

  # File activerecord/lib/active_record/base.rb, line 796
def inspect
  if self == Base
    super
  elsif abstract_class?
    "#{super}(abstract)"
  elsif table_exists?
    attr_list = columns.map { |c| "#{c.name}: #{c.type}" } * ', '
    "#{super}(#{attr_list})"
  else
    "#{super}(Table doesn't exist)"
  end
end
logger

Accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class, which is then passed on to any new database connections made and which can be retrieved on both a class and instance level by calling logger.

  # File activerecord/lib/active_record/base.rb, line 322
cattr_accessor :logger, :instance_writer => false
new(attributes = nil)

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 activerecord/lib/active_record/base.rb, line 1399
def initialize(attributes = nil)
  @attributes = attributes_from_column_definition
  @attributes_cache = {}
  @new_record = true
  @readonly = false
  @destroyed = false
  @marked_for_destruction = false
  @previously_changed = {}
  @changed_attributes = {}

  ensure_proper_type

  populate_with_current_scope_attributes
  self.attributes = attributes unless attributes.nil?

  result = yield self if block_given?
  _run_initialize_callbacks
  result
end
pluralize_table_names

Indicates whether table names should be the pluralized versions of the corresponding class names. If true, the default table name for a Product class will be products. If false, it would just be product. See table_name for the full rules on table/class naming. This is true, by default.

  # File activerecord/lib/active_record/base.rb, line 401
cattr_accessor :pluralize_table_names, :instance_writer => false
primary_key_prefix_type

Accessor for the prefix type that will be prepended to every primary key column name. The options are :table_name and :table_name_with_underscore. If the first is specified, the Product class will look for “productid” instead of “id” as the primary column. If the latter is specified, the Product class will look for “product_id” instead of “id”. Remember that this is a global setting for all Active Records.

  # File activerecord/lib/active_record/base.rb, line 373
cattr_accessor :primary_key_prefix_type, :instance_writer => false
quoted_table_name()

Returns a quoted version of the table name, used to construct SQL statements.

  # File activerecord/lib/active_record/base.rb, line 601
def quoted_table_name
  @quoted_table_name ||= connection.quote_table_name(table_name)
end
readonly_attributes()

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

  # File activerecord/lib/active_record/base.rb, line 532
def readonly_attributes
  read_inheritable_attribute(:attr_readonly) || []
end
remove_connection(klass = self)
  # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 105
def remove_connection(klass = self)
  connection_handler.remove_connection(klass)
end
reset_column_information()

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

The most common usage pattern for this method is probably in a migration, when just after creating a table you want to populate it with some default values, eg:

class CreateJobLevels < ActiveRecord::Migration
  def self.up
    create_table :job_levels do |t|
      t.integer :id
      t.string :name

      t.timestamps
    end

    JobLevel.reset_column_information
    %w{assistant executive manager director}.each do |type|
      JobLevel.create(:name => type)
    end
  end

  def self.down
    drop_table :job_levels
  end
end
  # File activerecord/lib/active_record/base.rb, line 747
def reset_column_information
  undefine_attribute_methods
  @column_names = @columns = @columns_hash = @content_columns = @dynamic_methods_hash = @inheritance_column = nil
  @arel_engine = @relation = @arel_table = nil
end
respond_to?(method_id, include_private = false)
  # File activerecord/lib/active_record/base.rb, line 841
def respond_to?(method_id, include_private = false)
  if match = DynamicFinderMatch.match(method_id)
    return true if all_attributes_exists?(match.attribute_names)
  elsif match = DynamicScopeMatch.match(method_id)
    return true if all_attributes_exists?(match.attribute_names)
  end

  super
end
retrieve_connection()
  # File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 96
def retrieve_connection
  connection_handler.retrieve_connection(self)
end
schema_format

Specifies the format to use when dumping the database schema with Rails’ Rakefile. If :sql, the schema is dumped as (potentially database- specific) SQL statements. If :ruby, the schema is dumped as an ActiveRecord::Schema file which can be loaded into any database that supports migrations. Use :ruby if you want to have different database adapters for, e.g., your development and test environments.

  # File activerecord/lib/active_record/base.rb, line 419
cattr_accessor :schema_format , :instance_writer => false
serialize(attr_name, class_name = Object)

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

Parameters

  • attr_name - The field name that should be serialized.

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

Example

# Serialize a preferences attribute
class User
  serialize :preferences
end
  # File activerecord/lib/active_record/base.rb, line 551
def serialize(attr_name, class_name = Object)
  serialized_attributes[attr_name.to_s] = class_name
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 activerecord/lib/active_record/base.rb, line 557
def serialized_attributes
  read_inheritable_attribute(:attr_serialized) or write_inheritable_attribute(:attr_serialized, {})
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.

class Project < ActiveRecord::Base
  set_inheritance_column do
    original_inheritance_column + "_id"
  end
end
This method is also aliased as inheritance_column=
  # File activerecord/lib/active_record/base.rb, line 653
def set_inheritance_column(value = nil, &block)
  define_attr_method :inheritance_column, value, &block
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.

class Project < ActiveRecord::Base
  set_sequence_name "projectseq"   # default would have been "project_seq"
end
This method is also aliased as sequence_name=
  # File activerecord/lib/active_record/base.rb, line 672
def set_sequence_name(value = nil, &block)
  define_attr_method :sequence_name, value, &block
end
set_table_name(value = nil, &block)

Sets the table name. If the value is nil or false then the value returned by the given block is used.

class Project < ActiveRecord::Base
  set_table_name "project"
end
This method is also aliased as table_name=
  # File activerecord/lib/active_record/base.rb, line 638
def set_table_name(value = nil, &block)
  @quoted_table_name = nil
  define_attr_method :table_name, value, &block
end
sti_name()
  # File activerecord/lib/active_record/base.rb, line 851
def sti_name
  store_full_sti_class ? name : name.demodulize
end
subclasses()
  # File activerecord/lib/active_record/base.rb, line 329
def subclasses
  descendants
end
table_exists?()

Indicates whether the table associated with this class exists

  # File activerecord/lib/active_record/base.rb, line 678
def table_exists?
  connection.table_exists?(table_name)
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::Base. So if the hierarchy looks like: Reply < Message < ActiveRecord::Base, then Message is used to guess the table name even when called on Reply. The rules used to do the guess are handled by the Inflector class in Active Support, which knows almost all common English inflections. You can add new inflections in config/initializers/inflections.rb.

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

Examples

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

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

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

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

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

class Mouse < ActiveRecord::Base
  set_table_name "mice"
end
  # File activerecord/lib/active_record/base.rb, line 596
def table_name
  reset_table_name
end
table_name_prefix

Accessor for the name of the prefix string to prepend to every table name. So if set to “basecamp_”, all table names will be named like “basecamp_projects”, “basecamp_people”, etc. This is a convenient way of creating a namespace for tables in a shared database. By default, the prefix is the empty string.

If you are organising your models within modules you can add a prefix to the models within a namespace by defining a singleton method in the parent module called table_name_prefix which returns your chosen prefix.

  # File activerecord/lib/active_record/base.rb, line 386
class_attribute :table_name_prefix, :instance_writer => false
table_name_suffix

Works like table_name_prefix, but appends instead of prepends (set to “_basecamp” gives “projects_basecamp”, “people_basecamp”). By default, the suffix is the empty string.

  # File activerecord/lib/active_record/base.rb, line 393
class_attribute :table_name_suffix, :instance_writer => false
timestamped_migrations

Specify whether or not to use timestamps for migration versions

  # File activerecord/lib/active_record/base.rb, line 425
cattr_accessor :timestamped_migrations , :instance_writer => false
Protected Class methods
aggregate_mapping(reflection)
  # File activerecord/lib/active_record/base.rb, line 1248
def aggregate_mapping(reflection)
  mapping = reflection.options[:mapping] || [reflection.name, reflection.name]
  mapping.first.is_a?(Array) ? mapping : [mapping]
end
class_of_active_record_descendant(klass)

Returns the class descending directly from ActiveRecord::Base or an abstract class, if any, in the inheritance hierarchy.

  # File activerecord/lib/active_record/base.rb, line 1211
def class_of_active_record_descendant(klass)
  if klass.superclass == Base || klass.superclass.abstract_class?
    klass
  elsif klass.superclass.nil?
    raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
  else
    class_of_active_record_descendant(klass.superclass)
  end
end
compute_type(type_name)

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

  # File activerecord/lib/active_record/base.rb, line 1183
def compute_type(type_name)
  if type_name.match(/^::/)
    # If the type is prefixed with a scope operator then we assume that
    # the type_name is an absolute reference.
    ActiveSupport::Dependencies.constantize(type_name)
  else
    # Build a list of candidates to search for
    candidates = []
    name.scan(/::|$/) { candidates.unshift "#{$`}::#{type_name}" }
    candidates << type_name

    candidates.each do |candidate|
      begin
        constant = ActiveSupport::Dependencies.constantize(candidate)
        return constant if candidate == constant.to_s
      rescue NameError => e
        # We don't want to swallow NoMethodError < NameError errors
        raise e unless e.instance_of?(NameError)
      rescue ArgumentError
      end
    end

    raise NameError, "uninitialized constant #{candidates.first}"
  end
end
default_scope(options = {})

Sets the default options for the model. The format of the options argument is the same as in find.

class Person < ActiveRecord::Base
  default_scope order('last_name, first_name')
end

default_scope is also applied while creating/building a record. It is not applied while updating a record.

class Article < ActiveRecord::Base
  default_scope where(:published => true)
end

Article.new.published    # => true
Article.create.published # => true
  # File activerecord/lib/active_record/base.rb, line 1168
def default_scope(options = {})
  reset_scoped_methods
  self.default_scoping << construct_finder_arel(options, default_scoping.pop)
end
expand_hash_conditions_for_aggregates(attrs)

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

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

Then:

{ :address => Address.new("813 abc st.", "chicago") }
  # => { :address_street => "813 abc st.", :address_city => "chicago" }
  # File activerecord/lib/active_record/base.rb, line 1264
def expand_hash_conditions_for_aggregates(attrs)
  expanded_attrs = {}
  attrs.each do |attr, value|
    unless (aggregation = reflect_on_aggregation(attr.to_sym)).nil?
      mapping = aggregate_mapping(aggregation)
      mapping.each do |field_attr, aggregate_attr|
        if mapping.size == 1 && !value.respond_to?(aggregate_attr)
          expanded_attrs[field_attr] = value
        else
          expanded_attrs[field_attr] = value.send(aggregate_attr)
        end
      end
    else
      expanded_attrs[attr] = value
    end
  end
  expanded_attrs
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 activerecord/lib/active_record/base.rb, line 1318
def sanitize_sql_array(ary)
  statement, *values = ary
  if values.first.is_a?(Hash) and statement =~ /:\w+/
    replace_named_bind_variables(statement, values.first)
  elsif statement.include?('?')
    replace_bind_variables(statement, values)
  elsif statement.blank?
    statement
  else
    statement % values.collect { |value| connection.quote_string(value.to_s) }
  end
end
sanitize_sql_for_assignment(assignments)

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

{ :name => nil, :group_id => 4 }  returns "name = NULL , group_id='4'"
  # File activerecord/lib/active_record/base.rb, line 1240
def sanitize_sql_for_assignment(assignments)
  case assignments
    when Array; sanitize_sql_array(assignments)
    when Hash;  sanitize_sql_hash_for_assignment(assignments)
    else        assignments
  end
end
sanitize_sql_for_conditions(condition, table_name = self.table_name)

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

["name='%s' and group_id='%s'", "foo'bar", 4]  returns  "name='foo''bar' and group_id='4'"
{ :name => "foo'bar", :group_id => 4 }  returns "name='foo''bar' and group_id='4'"
"name='foo''bar' and group_id='4'" returns "name='foo''bar' and group_id='4'"
This method is also aliased as sanitize_sql
  # File activerecord/lib/active_record/base.rb, line 1226
def sanitize_sql_for_conditions(condition, table_name = self.table_name)
  return nil if condition.blank?

  case condition
    when Array; sanitize_sql_array(condition)
    when Hash;  sanitize_sql_hash_for_conditions(condition, table_name)
    else        condition
  end
end
sanitize_sql_hash_for_assignment(attrs)

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

{ :status => nil, :group_id => 1 }
  # => "status = NULL , group_id = 1"
  # File activerecord/lib/active_record/base.rb, line 1309
def sanitize_sql_hash_for_assignment(attrs)
  attrs.map do |attr, value|
    "#{connection.quote_column_name(attr)} = #{quote_bound_value(value)}"
  end.join(', ')
end
sanitize_sql_hash_for_conditions(attrs, default_table_name = self.table_name)

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

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

And for value objects on a composed_of relationship:

{ :address => Address.new("123 abc st.", "chicago") }
  # => "address_street='123 abc st.' and address_city='chicago'"
This method is also aliased as sanitize_sql_hash
  # File activerecord/lib/active_record/base.rb, line 1297
def sanitize_sql_hash_for_conditions(attrs, default_table_name = self.table_name)
  attrs = expand_hash_conditions_for_aggregates(attrs)

  table = Arel::Table.new(self.table_name, :engine => arel_engine, :as => default_table_name)
  builder = PredicateBuilder.new(arel_engine)
  builder.build_from_hash(attrs, table).map{ |b| b.to_sql }.join(' AND ')
end
with_exclusive_scope(method_scoping = {}, &block)

Works like with_scope, but discards any nested properties.

  # File activerecord/lib/active_record/base.rb, line 1134
def with_exclusive_scope(method_scoping = {}, &block)
  if method_scoping.values.any? { |e| e.is_a?(ActiveRecord::Relation) }
    raise ArgumentError, New finder API can not be used with_exclusive_scope. You can either call unscoped to get an anonymous scope not bound to the default_scope:  User.unscoped.where(:active => true)Or call unscoped with a block:  User.unscoped do    User.where(:active => true).all  end
  end
  with_scope(method_scoping, :overwrite, &block)
end
with_scope(method_scoping = {}, action = :merge, &block)

with_scope lets you apply options to inner block incrementally. It takes a hash and the keys must be :find or :create. :find parameter is Relation while :create parameters are an attributes hash.

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

In nested scopings, all previous parameters are overwritten by the innermost rule, with the exception of where, includes, and joins operations in Relation, which are merged.

joins operations are uniqued so multiple scopes can join in the same table without table aliasing problems. If you need to join multiple tables, but still want one of the tables to be uniqued, use the array of strings format for your joins.

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

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

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

Note: the :find scope also has effect on update and deletion methods, like update_all and delete_all.

  # File activerecord/lib/active_record/base.rb, line 1093
def with_scope(method_scoping = {}, action = :merge, &block)
  method_scoping = method_scoping.method_scoping if method_scoping.respond_to?(:method_scoping)

  if method_scoping.is_a?(Hash)
    # Dup first and second level of hash (method and params).
    method_scoping = method_scoping.dup
    method_scoping.each do |method, params|
      method_scoping[method] = params.dup unless params == true
    end

    method_scoping.assert_valid_keys([ :find, :create ])
    relation = construct_finder_arel(method_scoping[:find] || {})

    if current_scoped_methods && current_scoped_methods.create_with_value && method_scoping[:create]
      scope_for_create = if action == :merge
        current_scoped_methods.create_with_value.merge(method_scoping[:create])
      else
        method_scoping[:create]
      end

      relation = relation.create_with(scope_for_create)
    else
      scope_for_create = method_scoping[:create]
      scope_for_create ||= current_scoped_methods.create_with_value if current_scoped_methods
      relation = relation.create_with(scope_for_create) if scope_for_create
    end

    method_scoping = relation
  end

  method_scoping = current_scoped_methods.merge(method_scoping) if current_scoped_methods && action ==  :merge

  self.scoped_methods << method_scoping
  begin
    yield
  ensure
    self.scoped_methods.pop
  end
end
Public Instance methods
==(comparison_object)

Returns true if comparison_object is the same exact object, or comparison_object is of the same type and self has an ID and it is equal to comparison_object.id.

Note that new records are different from any other record by definition, unless the other record is the receiver itself. Besides, if you fetch existing records with select and leave the ID out, you’re on your own, this predicate will return false.

Note also that destroying a record preserves its ID in the model instance, so deleted models are still comparable.

  # File activerecord/lib/active_record/base.rb, line 1624
def ==(comparison_object)
  comparison_object.equal?(self) ||
    (comparison_object.instance_of?(self.class) &&
      comparison_object.id == id && !comparison_object.new_record?)
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 activerecord/lib/active_record/base.rb, line 1523
def [](attr_name)
  read_attribute(attr_name)
end
[]=(attr_name, value)

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

  # File activerecord/lib/active_record/base.rb, line 1529
def []=(attr_name, value)
  write_attribute(attr_name, value)
end
attribute_for_inspect(attr_name)

Returns an inspect-like string for the value of the attribute attr_name. String attributes are elided after 50 characters, and Date and Time attributes are returned in the :db format. Other attributes return the value of inspect without modification.

person = Person.create!(:name => "David Heinemeier Hansson " * 3)

person.attribute_for_inspect(:name)
# => '"David Heinemeier Hansson David Heinemeier Hansson D..."'

person.attribute_for_inspect(:created_at)
# => '"2009-01-12 04:48:57"'
  # File activerecord/lib/active_record/base.rb, line 1591
def attribute_for_inspect(attr_name)
  value = read_attribute(attr_name)

  if value.is_a?(String) && value.length > 50
    "#{value[0..50]}...".inspect
  elsif value.is_a?(Date) || value.is_a?(Time)
    %("#{value.to_s(:db)}")
  else
    value.inspect
  end
end
attribute_names()

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

  # File activerecord/lib/active_record/base.rb, line 1516
def attribute_names
  @attributes.keys.sort
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 activerecord/lib/active_record/base.rb, line 1605
def attribute_present?(attribute)
  value = read_attribute(attribute)
  !value.blank?
end
attributes()

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

  # File activerecord/lib/active_record/base.rb, line 1572
def attributes
  attrs = {}
  attribute_names.each { |name| attrs[name] = read_attribute(name) }
  attrs
end
attributes=(new_attributes, guard_protected_attributes = true)

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).

If guard_protected_attributes is true (the default), then sensitive attributes can be protected from this form of mass-assignment by using the attr_protected macro. Or you can alternatively specify which attributes can be accessed with the attr_accessible macro. Then all the attributes not included in that won’t be allowed to be mass-assigned.

class User < ActiveRecord::Base
  attr_protected :is_admin
end

user = User.new
user.attributes = { :username => 'Phusion', :is_admin => true }
user.username   # => "Phusion"
user.is_admin?  # => false

user.send(:attributes=, { :username => 'Phusion', :is_admin => true }, false)
user.is_admin?  # => true
  # File activerecord/lib/active_record/base.rb, line 1553
def attributes=(new_attributes, guard_protected_attributes = true)
  return unless new_attributes.is_a?(Hash)
  attributes = new_attributes.stringify_keys

  multi_parameter_attributes = []
  attributes = sanitize_for_mass_assignment(attributes) if guard_protected_attributes

  attributes.each do |k, v|
    if k.include?("(")
      multi_parameter_attributes << [ k, v ]
    else
      respond_to?(:"#{k}=") ? send(:"#{k}=", v) : raise(UnknownAttributeError, "unknown attribute: #{k}")
    end
  end

  assign_multiparameter_attributes(multi_parameter_attributes)
end
cache_key()

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

Examples

Product.new.cache_key     # => "products/new"
Product.find(5).cache_key # => "products/5" (updated_at not available)
Person.find(5).cache_key  # => "people/5-20071224150000" (updated_at available)
  # File activerecord/lib/active_record/base.rb, line 1495
def cache_key
  case
  when new_record?
    "#{self.class.model_name.cache_key}/new"
  when timestamp = self[:updated_at]
    "#{self.class.model_name.cache_key}/#{id}-#{timestamp.to_s(:number)}"
  else
    "#{self.class.model_name.cache_key}/#{id}"
  end
end
column_for_attribute(name)

Returns the column object for the named attribute.

  # File activerecord/lib/active_record/base.rb, line 1611
def column_for_attribute(name)
  self.class.columns_hash[name.to_s]
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 activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 19
def connection
  self.class.connection
end
dup()

Returns duplicated record with unfreezed attributes.

  # File activerecord/lib/active_record/base.rb, line 1652
def dup
  obj = super
  obj.instance_variable_set('@attributes', @attributes.dup)
  obj
end
eql?(comparison_object)

Delegates to ==

  # File activerecord/lib/active_record/base.rb, line 1631
def eql?(comparison_object)
  self == (comparison_object)
end
freeze()

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

  # File activerecord/lib/active_record/base.rb, line 1642
def freeze
  @attributes.freeze; self
end
frozen?()

Returns true if the attributes hash has been frozen.

  # File activerecord/lib/active_record/base.rb, line 1647
def frozen?
  @attributes.frozen?
end
has_attribute?(attr_name)

Returns true if the given attribute is in the attributes hash

  # File activerecord/lib/active_record/base.rb, line 1511
def has_attribute?(attr_name)
  @attributes.has_key?(attr_name.to_s)
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 activerecord/lib/active_record/base.rb, line 1637
def hash
  id.hash
end
init_with(coder)

Initialize an empty model object from coder. coder must contain the attributes necessary for initializing an empty model object. For example:

class Post < ActiveRecord::Base
end

post = Post.allocate
post.init_with('attributes' => { 'title' => 'hello world' })
post.title # => 'hello world'
  # File activerecord/lib/active_record/base.rb, line 1453
def init_with(coder)
  @attributes = coder['attributes']
  @attributes_cache, @previously_changed, @changed_attributes = {}, {}, {}
  @new_record = @readonly = @destroyed = @marked_for_destruction = false
  _run_find_callbacks
  _run_initialize_callbacks
end
initialize_copy(other)

Cloned objects have no id assigned and are treated as new records. Note that this is a “shallow” clone as 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 activerecord/lib/active_record/base.rb, line 1422
def initialize_copy(other)
  _run_after_initialize_callbacks if respond_to?(:_run_after_initialize_callbacks)
  cloned_attributes = other.clone_attributes(:read_attribute_before_type_cast)
  cloned_attributes.delete(self.class.primary_key)

  @attributes = cloned_attributes

  @changed_attributes = {}
  attributes_from_column_definition.each do |attr, orig_value|
    @changed_attributes[attr] = orig_value if field_changed?(attr, orig_value, @attributes[attr])
  end

  clear_aggregation_cache
  clear_association_cache
  @attributes_cache = {}
  @new_record = true
  ensure_proper_type

  populate_with_current_scope_attributes
end
inspect()

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

  # File activerecord/lib/active_record/base.rb, line 1670
def inspect
  attributes_as_nice_string = self.class.column_names.collect { |name|
    if has_attribute?(name) || new_record?
      "#{name}: #{attribute_for_inspect(name)}"
    end
  }.compact.join(", ")
  "#<#{self.class} #{attributes_as_nice_string}>"
end
readonly!()

Marks this record as read only.

  # File activerecord/lib/active_record/base.rb, line 1665
def readonly!
  @readonly = true
end
readonly?()

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

  # File activerecord/lib/active_record/base.rb, line 1660
def readonly?
  @readonly
end
to_param()

Returns a String, which Action Pack uses for constructing an URL to this object. The default implementation returns this record’s id as a String, or nil if this record’s unsaved.

For example, suppose that you have a User model, and that you have a resources :users route. Normally, user_path will construct a path with the user object’s ‘id’ in it:

user = User.find_by_name('Phusion')
user_path(user)  # => "/users/1"

You can override to_param in your model to make user_path construct a path using the user’s name instead of the user’s id:

class User < ActiveRecord::Base
  def to_param  # overridden
    name
  end
end

user = User.find_by_name('Phusion')
user_path(user)  # => "/users/Phusion"
  # File activerecord/lib/active_record/base.rb, line 1483
def to_param
  # We can't use alias_method here, because method 'id' optimizes itself on the fly.
  id && id.to_s # Be sure to stringify the id for routes
end
Protected Instance methods
clone_attribute_value(reader_method, attribute_name)
  # File activerecord/lib/active_record/base.rb, line 1687
def clone_attribute_value(reader_method, attribute_name)
  value = send(reader_method, attribute_name)
  value.duplicable? ? value.clone : value
rescue TypeError, NoMethodError
  value
end
clone_attributes(reader_method = :read_attribute, attributes = {})
  # File activerecord/lib/active_record/base.rb, line 1680
def clone_attributes(reader_method = :read_attribute, attributes = {})
  attribute_names.each do |name|
    attributes[name] = clone_attribute_value(reader_method, name)
  end
  attributes
end