Methods

Instance Public methods

alias_attribute(new_name, old_name)

Allows you to make aliases for attributes.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_suffix '_short?'
  define_attribute_methods :name

  alias_attribute :nickname, :name

  private
    def attribute_short?(attr)
      send(attr).length < 5
    end
end

person = Person.new
person.name = 'Bob'
person.name            # => "Bob"
person.nickname        # => "Bob"
person.name_short?     # => true
person.nickname_short? # => true
📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 203
      def alias_attribute(new_name, old_name)
        old_name = old_name.to_s
        new_name = new_name.to_s
        self.attribute_aliases = attribute_aliases.merge(new_name => old_name)
        aliases_by_attribute_name[old_name] << new_name
        eagerly_generate_alias_attribute_methods(new_name, old_name)
      end
🔎 See on GitHub

attribute_alias(name)

Returns the original name for the alias name

📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 242
      def attribute_alias(name)
        attribute_aliases[name.to_s]
      end
🔎 See on GitHub

attribute_alias?(new_name)

Is new_name an alias?

📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 237
      def attribute_alias?(new_name)
        attribute_aliases.key? new_name.to_s
      end
🔎 See on GitHub

attribute_method_affix(*affixes)

Declares a method available for all attributes with the given prefix and suffix. Uses method_missing and respond_to? to rewrite the method.

#{prefix}#{attr}#{suffix}(*args, &block)

to

#{prefix}attribute#{suffix}(#{attr}, *args, &block)

An #{prefix}attribute#{suffix} instance method must exist and accept at least the attr argument.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_affix prefix: 'reset_', suffix: '_to_default!'
  define_attribute_methods :name

  private
    def reset_attribute_to_default!(attr)
      send("#{attr}=", 'Default Name')
    end
end

person = Person.new
person.name                         # => 'Gem'
person.reset_name_to_default!
person.name                         # => 'Default Name'
📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 175
      def attribute_method_affix(*affixes)
        self.attribute_method_patterns += affixes.map! { |affix| AttributeMethodPattern.new(**affix) }
        undefine_attribute_methods
      end
🔎 See on GitHub

attribute_method_prefix(*prefixes, parameters: nil)

Declares a method available for all attributes with the given prefix. Uses method_missing and respond_to? to rewrite the method.

#{prefix}#{attr}(*args, &block)

to

#{prefix}attribute(#{attr}, *args, &block)

An instance method #{prefix}attribute must exist and accept at least the attr argument.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_prefix 'clear_'
  define_attribute_methods :name

  private
    def clear_attribute(attr)
      send("#{attr}=", nil)
    end
end

person = Person.new
person.name = 'Bob'
person.name          # => "Bob"
person.clear_name
person.name          # => nil
📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 106
      def attribute_method_prefix(*prefixes, parameters: nil)
        self.attribute_method_patterns += prefixes.map! { |prefix| AttributeMethodPattern.new(prefix: prefix, parameters: parameters) }
        undefine_attribute_methods
      end
🔎 See on GitHub

attribute_method_suffix(*suffixes, parameters: nil)

Declares a method available for all attributes with the given suffix. Uses method_missing and respond_to? to rewrite the method.

#{attr}#{suffix}(*args, &block)

to

attribute#{suffix}(#{attr}, *args, &block)

An attribute#{suffix} instance method must exist and accept at least the attr argument.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_suffix '_short?'
  define_attribute_methods :name

  private
    def attribute_short?(attr)
      send(attr).length < 5
    end
end

person = Person.new
person.name = 'Bob'
person.name          # => "Bob"
person.name_short?   # => true
📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 140
      def attribute_method_suffix(*suffixes, parameters: nil)
        self.attribute_method_patterns += suffixes.map! { |suffix| AttributeMethodPattern.new(suffix: suffix, parameters: parameters) }
        undefine_attribute_methods
      end
🔎 See on GitHub

define_attribute_method(attr_name, _owner: generated_attribute_methods)

Declares an attribute that should be prefixed and suffixed by ActiveModel::AttributeMethods.

To use, pass an attribute name (as string or symbol). Be sure to declare define_attribute_method after you define any prefix, suffix or affix method, or they will not hook in.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_suffix '_short?'

  # Call to define_attribute_method must appear after the
  # attribute_method_prefix, attribute_method_suffix or
  # attribute_method_affix declarations.
  define_attribute_method :name

  private
    def attribute_short?(attr)
      send(attr).length < 5
    end
end

person = Person.new
person.name = 'Bob'
person.name        # => "Bob"
person.name_short? # => true
📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 308
      def define_attribute_method(attr_name, _owner: generated_attribute_methods)
        ActiveSupport::CodeGenerator.batch(_owner, __FILE__, __LINE__) do |owner|
          attribute_method_patterns.each do |pattern|
            method_name = pattern.method_name(attr_name)

            unless instance_method_already_implemented?(method_name)
              generate_method = "define_method_#{pattern.proxy_target}"

              if respond_to?(generate_method, true)
                send(generate_method, attr_name.to_s, owner: owner)
              else
                define_proxy_call(owner, method_name, pattern.proxy_target, pattern.parameters, attr_name.to_s, namespace: :active_model_proxy)
              end
            end
          end
          attribute_method_patterns_cache.clear
        end
      end
🔎 See on GitHub

define_attribute_methods(*attr_names)

Declares the attributes that should be prefixed and suffixed by ActiveModel::AttributeMethods.

To use, pass attribute names (as strings or symbols). Be sure to declare define_attribute_methods after you define any prefix, suffix, or affix methods, or they will not hook in.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name, :age, :address
  attribute_method_prefix 'clear_'

  # Call to define_attribute_methods must appear after the
  # attribute_method_prefix, attribute_method_suffix or
  # attribute_method_affix declarations.
  define_attribute_methods :name, :age, :address

  private
    def clear_attribute(attr)
      send("#{attr}=", nil)
    end
end
📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 269
      def define_attribute_methods(*attr_names)
        ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |owner|
          attr_names.flatten.each do |attr_name|
            define_attribute_method(attr_name, _owner: owner)
            aliases_by_attribute_name[attr_name.to_s].each do |aliased_name|
              generate_alias_attribute_methods owner, aliased_name, attr_name
            end
          end
        end
      end
🔎 See on GitHub

generate_alias_attribute_methods(code_generator, new_name, old_name)

📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 217
      def generate_alias_attribute_methods(code_generator, new_name, old_name)
        attribute_method_patterns.each do |pattern|
          alias_attribute_method_definition(code_generator, pattern, new_name, old_name)
        end
      end
🔎 See on GitHub

undefine_attribute_methods()

Removes all the previously dynamically defined methods from the class, including alias attribute methods.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_suffix '_short?'
  define_attribute_method :name
  alias_attribute :first_name, :name

  private
    def attribute_short?(attr)
      send(attr).length < 5
    end
end

person = Person.new
person.name = 'Bob'
person.first_name  # => "Bob"
person.name_short? # => true

Person.undefine_attribute_methods

person.name_short? # => NoMethodError
person.first_name  # => NoMethodError
📝 Source code 
# File activemodel/lib/active_model/attribute_methods.rb, line 352
      def undefine_attribute_methods
        generated_attribute_methods.module_eval do
          undef_method(*instance_methods)
        end
        attribute_method_patterns_cache.clear
      end
🔎 See on GitHub