Class: ActiveRecord::Base

Inherits:
Object show all
Defined in:
activerecord/lib/active_record/base.rb,
activerecord/lib/active_record/connection_adapters/mysql_adapter.rb,
activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb,
activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb,
activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb

Overview

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.

Defined Under Namespace

Classes: ConnectionSpecification

Constant Summary

@@configurations = 
{}
@@primary_key_prefix_type = 
nil
@@pluralize_table_names = 
true
@@default_timezone = 
:local
@@schema_format = 
:ruby
@@timestamped_migrations = 
true

Class Attribute Summary (collapse)

Class Method Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (Base) initialize(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. 



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# File 'activerecord/lib/active_record/base.rb', line 1395

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

  if scope = self.class.send(:current_scoped_methods)
    create_with = scope.scope_for_create
    create_with.each { |att,value| self.send("#{att}=", value) } if create_with
  end
  self.attributes = attributes unless attributes.nil?

  result = yield self if block_given?
  _run_initialize_callbacks
  result
end

Class Attribute Details

+ (Object) abstract_class

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



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# File 'activerecord/lib/active_record/base.rb', line 828

def abstract_class
  @abstract_class
end

Class Method Details

+ (Object) ===(object)

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



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# File 'activerecord/lib/active_record/base.rb', line 813

def ===(object)
  object.is_a?(self)
end

+ (Boolean) abstract_class?

Returns whether this class is an abstract class or not.

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 831

def abstract_class?
  defined?(@abstract_class) && @abstract_class == true
end

+ (Object) arel_engine 



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# File 'activerecord/lib/active_record/base.rb', line 853

def arel_engine
  @arel_engine ||= begin
    if self == ActiveRecord::Base
      Arel::Table.engine
    else
      connection_handler.connection_pools[name] ? Arel::Sql::Engine.new(self) : superclass.arel_engine
    end
  end
end

+ (Object) arel_table 



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# File 'activerecord/lib/active_record/base.rb', line 849

def arel_table
  @arel_table ||= Arel::Table.new(table_name, arel_engine)
end

+ (Object) attr_readonly(*attributes)

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



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# File 'activerecord/lib/active_record/base.rb', line 521

def attr_readonly(*attributes)
  write_inheritable_attribute(:attr_readonly, Set.new(attributes.map { |a| a.to_s }) + (readonly_attributes || []))
end

+ (Boolean) attribute_method?(attribute)

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 751

def attribute_method?(attribute)
  super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, '')))
end

+ (Object) 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. 



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# File 'activerecord/lib/active_record/base.rb', line 823

def base_class
  class_of_active_record_descendant(self)
end

+ (Object) colorize_logging(*args) Also known as: colorize_logging= 



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# File 'activerecord/lib/active_record/base.rb', line 432

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

+ (Object) column_methods_hash

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



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# File 'activerecord/lib/active_record/base.rb', line 704

def column_methods_hash #:nodoc:
  @dynamic_methods_hash ||= column_names.inject(Hash.new(false)) do |methods, attr|
    attr_name = attr.to_s
    methods[attr.to_sym]       = attr_name
    methods["#{attr}=".to_sym] = attr_name
    methods["#{attr}?".to_sym] = attr_name
    methods["#{attr}_before_type_cast".to_sym] = attr_name
    methods
  end
end

+ (Object) column_names

Returns an array of column names as strings. 



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# File 'activerecord/lib/active_record/base.rb', line 691

def column_names
  @column_names ||= columns.map { |column| column.name }
end

+ (Object) columns

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



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# File 'activerecord/lib/active_record/base.rb', line 677

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

+ (Object) columns_hash

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



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# File 'activerecord/lib/active_record/base.rb', line 686

def columns_hash
  @columns_hash ||= columns.inject({}) { |hash, column| hash[column.name] = column; hash }
end

+ (Boolean) connected?

Returns true if Active Record is connected.

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb', line 101

def connected?
  connection_handler.connected?(self)
end

+ (Object) 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. 



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# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb', line 88

def connection
  retrieve_connection
end

+ (Object) connection_pool 



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# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb', line 92

def connection_pool
  connection_handler.retrieve_connection_pool(self)
end

+ (Object) 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. 



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# File 'activerecord/lib/active_record/base.rb', line 697

def content_columns
  @content_columns ||= columns.reject { |c| c.primary || c.name =~ /(_id|_count)$/ || c.name == inheritance_column }
end

+ (Object) 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"



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# File 'activerecord/lib/active_record/base.rb', line 514

def count_by_sql(sql)
  sql = sanitize_conditions(sql)
  connection.select_value(sql, "#{name} Count").to_i
end

+ (Object) 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



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# File 'activerecord/lib/active_record/base.rb', line 492

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

+ (Boolean) descends_from_active_record?

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

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 776

def descends_from_active_record?
  if superclass.abstract_class?
    superclass.descends_from_active_record?
  else
    superclass == Base || !columns_hash.include?(inheritance_column)
  end
end

+ (Object) 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. 



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# 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
        raise "Please install the #{spec[:adapter]} adapter: `gem install activerecord-#{spec[:adapter]}-adapter` (#{$!})"
      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

+ (Object) 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"}>, ...]



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# File 'activerecord/lib/active_record/base.rb', line 466

def find_by_sql(sql)
  connection.select_all(sanitize_sql(sql), "#{name} Load").collect! { |record| instantiate(record) }
end

+ (Boolean) finder_needs_type_condition?

:nodoc:

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 784

def finder_needs_type_condition? #:nodoc:
  # This is like this because benchmarking justifies the strange :false stuff
  :true == (@finder_needs_type_condition ||= descends_from_active_record? ? :false : :true)
end

+ (Object) full_table_name_prefix

:nodoc: 



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# File 'activerecord/lib/active_record/base.rb', line 604

def full_table_name_prefix #:nodoc:
  (parents.detect{ |p| p.respond_to?(:table_name_prefix) } || self).table_name_prefix
end

+ (Object) i18n_scope

Set the i18n scope to overwrite ActiveModel. 



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# File 'activerecord/lib/active_record/base.rb', line 771

def i18n_scope #:nodoc:
  :activerecord
end

+ (Object) inheritance_column

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



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# File 'activerecord/lib/active_record/base.rb', line 610

def inheritance_column
  @inheritance_column ||= "type".freeze
end

+ (Object) inspect

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



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# File 'activerecord/lib/active_record/base.rb', line 790

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

+ (Object) lookup_ancestors

Set the lookup ancestors for ActiveModel. 



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# File 'activerecord/lib/active_record/base.rb', line 756

def lookup_ancestors #:nodoc:
  klass = self
  classes = [klass]
  while klass != klass.base_class
    classes << klass = klass.superclass
  end
  classes
rescue
  # OPTIMIZE this rescue is to fix this test: ./test/cases/reflection_test.rb:56:in `test_human_name_for_column'
  # Apparently the method base_class causes some trouble.
  # It now works for sure.
  [self]
end

+ (Object) mysql_connection(config)

Establishes a connection to the database that’s used by all Active Record objects. 



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# File 'activerecord/lib/active_record/connection_adapters/mysql_adapter.rb', line 9

def self.mysql_connection(config) # :nodoc:
  config = config.symbolize_keys
  host     = config[:host]
  port     = config[:port]
  socket   = config[:socket]
  username = config[:username] ? config[:username].to_s : 'root'
  password = config[:password].to_s
  database = config[:database]

  unless defined? Mysql
    begin
      require 'mysql'
    rescue LoadError
      raise "!!! Missing the mysql gem. Add it to your Gemfile: gem 'mysql', '2.8.1'"
    end

    unless defined?(Mysql::Result) && Mysql::Result.method_defined?(:each_hash)
      raise "!!! Outdated mysql gem. Upgrade to 2.8.1 or later. In your Gemfile: gem 'mysql', '2.8.1'"
    end
  end

  mysql = Mysql.init
  mysql.ssl_set(config[:sslkey], config[:sslcert], config[:sslca], config[:sslcapath], config[:sslcipher]) if config[:sslca] || config[:sslkey]

  default_flags = Mysql.const_defined?(:CLIENT_MULTI_RESULTS) ? Mysql::CLIENT_MULTI_RESULTS : 0
  default_flags |= Mysql::CLIENT_FOUND_ROWS if Mysql.const_defined?(:CLIENT_FOUND_ROWS)
  options = [host, username, password, database, port, socket, default_flags]
  ConnectionAdapters::MysqlAdapter.new(mysql, logger, options, config)
end

+ (Object) postgresql_connection(config)

Establishes a connection to the database that’s used by all Active Record objects 



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# File 'activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb', line 8

def self.postgresql_connection(config) # :nodoc:
  require 'pg'

  config = config.symbolize_keys
  host     = config[:host]
  port     = config[:port] || 5432
  username = config[:username].to_s if config[:username]
  password = config[:password].to_s if config[:password]

  if config.has_key?(:database)
    database = config[:database]
  else
    raise ArgumentError, "No database specified. Missing argument: database."
  end

  # The postgres drivers don't allow the creation of an unconnected PGconn object,
  # so just pass a nil connection object for the time being.
  ConnectionAdapters::PostgreSQLAdapter.new(nil, logger, [host, port, nil, nil, database, username, password], config)
end

+ (Object) quote_value(value, column = nil)

:nodoc: 



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# File 'activerecord/lib/active_record/base.rb', line 803

def quote_value(value, column = nil) #:nodoc:
  connection.quote(value,column)
end

+ (Object) quoted_table_name

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



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# File 'activerecord/lib/active_record/base.rb', line 595

def quoted_table_name
  @quoted_table_name ||= connection.quote_table_name(table_name)
end

+ (Object) readonly_attributes

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



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# File 'activerecord/lib/active_record/base.rb', line 526

def readonly_attributes
  read_inheritable_attribute(:attr_readonly) || []
end

+ (Object) remove_connection(klass = self) 



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# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb', line 105

def remove_connection(klass = self)
  connection_handler.remove_connection(klass)
end

+ (Object) 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



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# File 'activerecord/lib/active_record/base.rb', line 741

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

+ (Object) reset_column_information_and_inheritable_attributes_for_all_subclasses

:nodoc: 



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# File 'activerecord/lib/active_record/base.rb', line 747

def reset_column_information_and_inheritable_attributes_for_all_subclasses#:nodoc:
  descendants.each { |klass| klass.reset_inheritable_attributes; klass.reset_column_information }
end

+ (Object) reset_sequence_name

:nodoc: 



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# File 'activerecord/lib/active_record/base.rb', line 620

def reset_sequence_name #:nodoc:
  default = connection.default_sequence_name(table_name, primary_key)
  set_sequence_name(default)
  default
end

+ (Object) reset_subclasses

:nodoc: 



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# File 'activerecord/lib/active_record/base.rb', line 320

def reset_subclasses #:nodoc:
  ActiveSupport::Deprecation.warn 'ActiveRecord::Base.reset_subclasses no longer does anything in Rails 3. It will be removed in the final release; please update your apps and plugins.', caller
end

+ (Object) reset_table_name

Computes the table name, (re)sets it internally, and returns it. 



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# File 'activerecord/lib/active_record/base.rb', line 600

def reset_table_name #:nodoc:
  self.table_name = compute_table_name
end

+ (Boolean) respond_to?(method_id, include_private = false)

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 835

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

+ (Object) retrieve_connection 



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# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb', line 96

def retrieve_connection
  connection_handler.retrieve_connection(self)
end

+ (Object) sanitize(object)

Used to sanitize objects before they’re used in an SQL SELECT statement. Delegates to connection.quote. 



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# File 'activerecord/lib/active_record/base.rb', line 808

def sanitize(object) #:nodoc:
  connection.quote(object)
end

+ (Object) scoped_methods

:nodoc: 



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# File 'activerecord/lib/active_record/base.rb', line 888

def scoped_methods #:nodoc:
  key = :#{self}_scoped_methods"
  Thread.current[key] = Thread.current[key].presence || self.default_scoping.dup
end

+ (Object) sequence_name

Lazy-set the sequence name to the connection’s default. This method is only ever called once since set_sequence_name overrides it. 



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# File 'activerecord/lib/active_record/base.rb', line 616

def sequence_name #:nodoc:
  reset_sequence_name
end

+ (Object) 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



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# File 'activerecord/lib/active_record/base.rb', line 545

def serialize(attr_name, class_name = Object)
  serialized_attributes[attr_name.to_s] = class_name
end

+ (Object) serialized_attributes

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



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# File 'activerecord/lib/active_record/base.rb', line 551

def serialized_attributes
  read_inheritable_attribute(:attr_serialized) or write_inheritable_attribute(:attr_serialized, {})
end

+ (Object) set_inheritance_column(value = nil, &block) Also known as: inheritance_column=

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



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# File 'activerecord/lib/active_record/base.rb', line 647

def set_inheritance_column(value = nil, &block)
  define_attr_method :inheritance_column, value, &block
end

+ (Object) set_sequence_name(value = nil, &block) Also known as: sequence_name=

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



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# File 'activerecord/lib/active_record/base.rb', line 666

def set_sequence_name(value = nil, &block)
  define_attr_method :sequence_name, value, &block
end

+ (Object) set_table_name(value = nil, &block) Also known as: table_name=

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



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# File 'activerecord/lib/active_record/base.rb', line 632

def set_table_name(value = nil, &block)
  @quoted_table_name = nil
  define_attr_method :table_name, value, &block
end

+ (Object) sqlite3_connection(config)

sqlite3 adapter reuses sqlite_connection. 



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# File 'activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb', line 6

def self.sqlite3_connection(config) # :nodoc:
  # Require database.
  unless config[:database]
    raise ArgumentError, "No database file specified. Missing argument: database"
  end

  # Allow database path relative to Rails.root, but only if
  # the database path is not the special path that tells
  # Sqlite to build a database only in memory.
  if defined?(Rails.root) && ':memory:' != config[:database]
    config[:database] = File.expand_path(config[:database], Rails.root)
  end

  unless 'sqlite3' == config[:adapter]
    raise ArgumentError, 'adapter name should be "sqlite3"'
  end

  unless self.class.const_defined?(:SQLite3)
    require_library_or_gem(config[:adapter])
  end

  db = SQLite3::Database.new(
    config[:database],
    :results_as_hash => true
  )

  db.busy_timeout(config[:timeout]) unless config[:timeout].nil?

  ConnectionAdapters::SQLite3Adapter.new(db, logger, config)
end

+ (Object) sti_name 



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# File 'activerecord/lib/active_record/base.rb', line 845

def sti_name
  store_full_sti_class ? name : name.demodulize
end

+ (Object) subclasses 



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# File 'activerecord/lib/active_record/base.rb', line 324

def subclasses
  descendants
end

+ (Boolean) table_exists?

Indicates whether the table associated with this class exists

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 672

def table_exists?
  connection.table_exists?(table_name)
end

+ (Object) 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



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# File 'activerecord/lib/active_record/base.rb', line 590

def table_name
  reset_table_name
end

+ (Object) unscoped

Returns a scope for this class without taking into account the default_scope. 

  class Post < ActiveRecord::Base
    default_scope :published => true
  end

  Post.all          # Fires "SELECT * FROM posts WHERE published = true"
  Post.unscoped.all # Fires "SELECT * FROM posts"

This method also accepts a block meaning that all queries inside the block will not use the default_scope: 

  Post.unscoped {
    limit(10) # Fires "SELECT * FROM posts LIMIT 10"
  }

It is recommended to use block form of unscoped because chaining unscoped with named_scope does not work. Assuming that published is a named_scope following two statements are same.

Post.unscoped.published Post.published 



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# File 'activerecord/lib/active_record/base.rb', line 884

def unscoped #:nodoc:
  block_given? ? relation.scoping { yield } : relation
end

Instance Method Details

- (Object) ==(comparison_object)

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



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# File 'activerecord/lib/active_record/base.rb', line 1600

def ==(comparison_object)
  comparison_object.equal?(self) ||
    (comparison_object.instance_of?(self.class) &&
      comparison_object.id == id && !comparison_object.new_record?)
end

- (Object) [](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). 



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# File 'activerecord/lib/active_record/base.rb', line 1507

def [](attr_name)
  read_attribute(attr_name)
end

- (Object) []=(attr_name, value)

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



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# File 'activerecord/lib/active_record/base.rb', line 1513

def []=(attr_name, value)
  write_attribute(attr_name, value)
end

- (Object) 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"'



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# File 'activerecord/lib/active_record/base.rb', line 1575

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

- (Object) attribute_names

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



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# File 'activerecord/lib/active_record/base.rb', line 1500

def attribute_names
  @attributes.keys.sort
end

- (Boolean) 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).

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 1589

def attribute_present?(attribute)
  value = read_attribute(attribute)
  !value.blank?
end

- (Object) attributes

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



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# File 'activerecord/lib/active_record/base.rb', line 1556

def attributes
  attrs = {}
  attribute_names.each { |name| attrs[name] = read_attribute(name) }
  attrs
end

- (Object) 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



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# File 'activerecord/lib/active_record/base.rb', line 1537

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

- (Object) 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)



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# File 'activerecord/lib/active_record/base.rb', line 1479

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

- (Object) column_for_attribute(name)

Returns the column object for the named attribute. 



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# File 'activerecord/lib/active_record/base.rb', line 1595

def column_for_attribute(name)
  self.class.columns_hash[name.to_s]
end

- (Object) 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. 



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# File 'activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb', line 19

def connection
  self.class.connection
end

- (Object) dup

Returns duplicated record with unfreezed attributes. 



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# File 'activerecord/lib/active_record/base.rb', line 1628

def dup
  obj = super
  obj.instance_variable_set('@attributes', @attributes.dup)
  obj
end

- (Boolean) eql?(comparison_object)

Delegates to ==

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 1607

def eql?(comparison_object)
  self == (comparison_object)
end

- (Object) freeze

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



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# File 'activerecord/lib/active_record/base.rb', line 1618

def freeze
  @attributes.freeze; self
end

- (Boolean) frozen?

Returns true if the attributes hash has been frozen.

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 1623

def frozen?
  @attributes.frozen?
end

- (Boolean) has_attribute?(attr_name)

Returns true if the given attribute is in the attributes hash

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 1495

def has_attribute?(attr_name)
  @attributes.has_key?(attr_name.to_s)
end

- (Object) 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) ]



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# File 'activerecord/lib/active_record/base.rb', line 1613

def hash
  id.hash
end

- (Object) 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. 



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# File 'activerecord/lib/active_record/base.rb', line 1421

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

  if scope = self.class.send(:current_scoped_methods)
    create_with = scope.scope_for_create
    create_with.each { |att,value| self.send("#{att}=", value) } if create_with
  end
end

- (Object) inspect

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



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# File 'activerecord/lib/active_record/base.rb', line 1646

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

- (Object) quoted_id

:nodoc: 



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# File 'activerecord/lib/active_record/base.rb', line 1490

def quoted_id #:nodoc:
  quote_value(id, column_for_attribute(self.class.primary_key))
end

- (Object) readonly!

Marks this record as read only. 



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# File 'activerecord/lib/active_record/base.rb', line 1641

def readonly!
  @readonly = true
end

- (Boolean) 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.

Returns:

  • (Boolean) 


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# File 'activerecord/lib/active_record/base.rb', line 1636

def readonly?
  @readonly
end

- (Object) 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"



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# File 'activerecord/lib/active_record/base.rb', line 1467

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