module ActiveModel::AttributeMethods::ClassMethods

Public Instance Methods

alias_attribute(new_name, old_name) click to toggle source

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
# File lib/active_model/attribute_methods.rb, line 204
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
attribute_alias(name) click to toggle source

Returns the original name for the alias name

# File lib/active_model/attribute_methods.rb, line 258
def attribute_alias(name)
  attribute_aliases[name.to_s]
end
attribute_alias?(new_name) click to toggle source

Is new_name an alias?

# File lib/active_model/attribute_methods.rb, line 253
def attribute_alias?(new_name)
  attribute_aliases.key? new_name.to_s
end
attribute_method_affix(*affixes) click to toggle source

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'
# File lib/active_model/attribute_methods.rb, line 176
def attribute_method_affix(*affixes)
  self.attribute_method_patterns += affixes.map! { |affix| AttributeMethodPattern.new(**affix) }
  undefine_attribute_methods
end
attribute_method_prefix(*prefixes, parameters: nil) click to toggle source

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
# File lib/active_model/attribute_methods.rb, line 107
def attribute_method_prefix(*prefixes, parameters: nil)
  self.attribute_method_patterns += prefixes.map! { |prefix| AttributeMethodPattern.new(prefix: prefix, parameters: parameters) }
  undefine_attribute_methods
end
attribute_method_suffix(*suffixes, parameters: nil) click to toggle source

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
# File lib/active_model/attribute_methods.rb, line 141
def attribute_method_suffix(*suffixes, parameters: nil)
  self.attribute_method_patterns += suffixes.map! { |suffix| AttributeMethodPattern.new(suffix: suffix, parameters: parameters) }
  undefine_attribute_methods
end
define_attribute_method(attr_name, _owner: generated_attribute_methods) click to toggle source

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
# File lib/active_model/attribute_methods.rb, line 324
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
define_attribute_methods(*attr_names) click to toggle source

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
# File lib/active_model/attribute_methods.rb, line 285
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
generate_alias_attribute_methods(code_generator, new_name, old_name) click to toggle source
# File lib/active_model/attribute_methods.rb, line 218
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
undefine_attribute_methods() click to toggle source

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
# File lib/active_model/attribute_methods.rb, line 368
def undefine_attribute_methods
  generated_attribute_methods.module_eval do
    undef_method(*instance_methods)
  end
  attribute_method_patterns_cache.clear
end

Private Instance Methods

attribute_method_patterns_cache() click to toggle source

The methods method_missing and respond_to? of this module are invoked often in a typical rails, both of which invoke the method matched_attribute_method. The latter method iterates through an array doing regular expression matches, which results in a lot of object creations. Most of the time it returns a nil match. As the match result is always the same given a method_name, this cache is used to alleviate the GC, which ultimately also speeds up the app significantly (in our case our test suite finishes 10% faster with this cache).

# File lib/active_model/attribute_methods.rb, line 408
def attribute_method_patterns_cache
  @attribute_method_patterns_cache ||= Concurrent::Map.new(initial_capacity: 4)
end
attribute_method_patterns_matching(method_name) click to toggle source
# File lib/active_model/attribute_methods.rb, line 412
def attribute_method_patterns_matching(method_name)
  attribute_method_patterns_cache.compute_if_absent(method_name) do
    attribute_method_patterns.filter_map { |pattern| pattern.match(method_name) }
  end
end
define_proxy_call(code_generator, name, proxy_target, parameters, *call_args, namespace:) click to toggle source

Define a method ‘name` in `mod` that dispatches to `send` using the given `extra` args. This falls back on `send` if the called name cannot be compiled.

# File lib/active_model/attribute_methods.rb, line 421
def define_proxy_call(code_generator, name, proxy_target, parameters, *call_args, namespace:)
  mangled_name = name
  unless NAME_COMPILABLE_REGEXP.match?(name)
    mangled_name = "__temp__#{name.unpack1("h*")}"
  end

  call_args.map!(&:inspect)
  call_args << parameters if parameters
  namespace = :"#{namespace}_#{proxy_target}_#{call_args.join("_")}}"

  code_generator.define_cached_method(name, as: mangled_name, namespace: namespace) do |batch|
    body = if CALL_COMPILABLE_REGEXP.match?(proxy_target)
      "self.#{proxy_target}(#{call_args.join(", ")})"
    else
      call_args.unshift(":'#{proxy_target}'")
      "send(#{call_args.join(", ")})"
    end

    modifier = parameters == FORWARD_PARAMETERS ? "ruby2_keywords " : ""

    batch <<
      "#{modifier}def #{mangled_name}(#{parameters || ''})" <<
      body <<
      "end"
  end
end
generated_attribute_methods() click to toggle source
# File lib/active_model/attribute_methods.rb, line 391
def generated_attribute_methods
  @generated_attribute_methods ||= Module.new.tap { |mod| include mod }
end
instance_method_already_implemented?(method_name) click to toggle source
# File lib/active_model/attribute_methods.rb, line 395
def instance_method_already_implemented?(method_name)
  generated_attribute_methods.method_defined?(method_name)
end
resolve_attribute_name(name) click to toggle source
Calls superclass method
# File lib/active_model/attribute_methods.rb, line 387
def resolve_attribute_name(name)
  attribute_aliases.fetch(super, &:itself)
end