Module: ActiveRecord::AttributeMethods

Extended by:
ActiveSupport::Autoload, ActiveSupport::Concern
Includes:
ActiveModel::AttributeMethods
Included in:
Base
Defined in:
activerecord/lib/active_record/attribute_methods.rb,
activerecord/lib/active_record.rb,
activerecord/lib/active_record/attribute_methods/read.rb,
activerecord/lib/active_record/attribute_methods/query.rb,
activerecord/lib/active_record/attribute_methods/dirty.rb,
activerecord/lib/active_record/attribute_methods/write.rb,
activerecord/lib/active_record/attribute_methods/primary_key.rb,
activerecord/lib/active_record/attribute_methods/serialization.rb,
activerecord/lib/active_record/attribute_methods/before_type_cast.rb,
activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb

Overview

Active Record Attribute Methods

Defined Under Namespace

Modules: BeforeTypeCast, ClassMethods, Dirty, PrimaryKey, Query, Read, Serialization, TimeZoneConversion, Write Classes: AttributeMethodCache

Constant Summary

AttrNames =
Module.new {
  def self.set_name_cache(name, value)
    const_name = "ATTR_#{name}"
    unless const_defined? const_name
      const_set const_name, value.dup.freeze
    end
  end
}
BLACKLISTED_CLASS_METHODS =
%w(private public protected)

Constants included from ActiveModel::AttributeMethods

ActiveModel::AttributeMethods::CALL_COMPILABLE_REGEXP, ActiveModel::AttributeMethods::NAME_COMPILABLE_REGEXP

Instance Method Summary (collapse)

Methods included from ActiveSupport::Concern

append_features, class_methods, extended, included

Methods included from ActiveSupport::Autoload

autoload, autoload_at, autoload_under, autoloads, eager_autoload, eager_load!, extended

Methods included from ActiveModel::AttributeMethods

#attribute_missing, #respond_to_without_attributes?

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

- (Object) method_missing(method, *args, &block)

If we haven't generated any methods yet, generate them, then see if we've created the method we're looking for.



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 194

def method_missing(method, *args, &block) # :nodoc:
  self.class.define_attribute_methods
  if respond_to_without_attributes?(method)
    # make sure to invoke the correct attribute method, as we might have gotten here via a `super`
    # call in a overwritten attribute method
    if attribute_method = self.class.find_generated_attribute_method(method)
      # this is probably horribly slow, but should only happen at most once for a given AR class
      attribute_method.bind(self).call(*args, &block)
    else
      send(method, *args, &block)
    end
  else
    super
  end
end

Instance Method Details

- (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 date column is cast to a date object, like Date.new(2004, 12, 12)). It raises ActiveModel::MissingAttributeError if the identified attribute is missing.

Alias for the read_attribute method.

class Person < ActiveRecord::Base
  belongs_to :organization
end

person = Person.new(name: 'Francesco', age: '22')
person[:name] # => "Francesco"
person[:age]  # => 22

person = Person.select('id').first
person[:name]            # => ActiveModel::MissingAttributeError: missing attribute: name
person[:organization_id] # => ActiveModel::MissingAttributeError: missing attribute: organization_id


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 375

def [](attr_name)
  read_attribute(attr_name) { |n| missing_attribute(n, caller) }
end

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

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

class Person < ActiveRecord::Base
end

person = Person.new
person[:age] = '22'
person[:age] # => 22
person[:age] # => Fixnum


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 389

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 truncated upto 50 characters, Date and Time attributes are returned in the :db format, Array attributes are truncated upto 10 values. 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 ...\""

person.attribute_for_inspect(:created_at)
# => "\"2012-10-22 00:15:07\""

person.attribute_for_inspect(:tag_ids)
# => "[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, ...]"


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 306

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)}")
  elsif value.is_a?(Array) && value.size > 10
    inspected = value.first(10).inspect
    %(#{inspected[0...-1]}, ...])
  else
    value.inspect
  end
end

- (Object) attribute_names

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

class Person < ActiveRecord::Base
end

person = Person.new
person.attribute_names
# => ["id", "created_at", "updated_at", "name", "age"]


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 266

def attribute_names
  @attributes.keys
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). Otherwise, false. Note that it always returns true with boolean attributes.

class Task < ActiveRecord::Base
end

person = Task.new(title: '', is_done: false)
person.attribute_present?(:title)   # => false
person.attribute_present?(:is_done) # => true
person.name = 'Francesco'
person.is_done = true
person.attribute_present?(:title)   # => true
person.attribute_present?(:is_done) # => true


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 336

def attribute_present?(attribute)
  value = read_attribute(attribute)
  !value.nil? && !(value.respond_to?(:empty?) && value.empty?)
end

- (Object) attributes

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

class Person < ActiveRecord::Base
end

person = Person.create(name: 'Francesco', age: 22)
person.attributes
# => {"id"=>3, "created_at"=>Sun, 21 Oct 2012 04:53:04, "updated_at"=>Sun, 21 Oct 2012 04:53:04, "name"=>"Francesco", "age"=>22}


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 278

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

- (Object) attributes_for_coder

Placeholder so it can be overriden when needed by serialization



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# File 'activerecord/lib/active_record/attribute_methods.rb', line 285

def attributes_for_coder # :nodoc:
  attributes
end

- (Object) column_for_attribute(name)

Returns the column object for the named attribute. Returns nil if the named attribute not exists.

class Person < ActiveRecord::Base
end

person = Person.new
person.column_for_attribute(:name) # the result depends on the ConnectionAdapter
# => #<ActiveRecord::ConnectionAdapters::SQLite3Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...>

person.column_for_attribute(:nothing)
# => nil


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 353

def column_for_attribute(name)
  # FIXME: should this return a null object for columns that don't exist?
  self.class.columns_hash[name.to_s]
end

- (Boolean) has_attribute?(attr_name)

Returns true if the given attribute is in the attributes hash, otherwise false.

class Person < ActiveRecord::Base
end

person = Person.new
person.has_attribute?(:name)    # => true
person.has_attribute?('age')    # => true
person.has_attribute?(:nothing) # => false


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 254

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

- (Boolean) respond_to?(name, include_private = false)

A Person object with a name attribute can ask person.respond_to?(:name), person.respond_to?(:name=), and person.respond_to?(:name?) which will all return true. It also define the attribute methods if they have not been generated.

class Person < ActiveRecord::Base
end

person = Person.new
person.respond_to(:name)    # => true
person.respond_to(:name=)   # => true
person.respond_to(:name?)   # => true
person.respond_to('age')    # => true
person.respond_to('age=')   # => true
person.respond_to('age?')   # => true
person.respond_to(:nothing) # => false


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# File 'activerecord/lib/active_record/attribute_methods.rb', line 226

def respond_to?(name, include_private = false)
  name = name.to_s
  self.class.define_attribute_methods
  result = super

  # If the result is false the answer is false.
  return false unless result

  # If the result is true then check for the select case.
  # For queries selecting a subset of columns, return false for unselected columns.
  # We check defined?(@attributes) not to issue warnings if called on objects that
  # have been allocated but not yet initialized.
  if defined?(@attributes) && @attributes.any? && self.class.column_names.include?(name)
    return has_attribute?(name)
  end

  return true
end