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 207
def alias_attribute(new_name, old_name)
  self.attribute_aliases = attribute_aliases.merge(new_name.to_s => old_name.to_s)
  attribute_method_matchers.each do |matcher|
    matcher_new = matcher.method_name(new_name).to_s
    matcher_old = matcher.method_name(old_name).to_s
    define_proxy_call false, self, matcher_new, matcher_old
  end
end
attribute_alias(name) click to toggle source

Returns the original name for the alias name

# File lib/active_model/attribute_methods.rb, line 222
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 217
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 178
def attribute_method_affix(*affixes)
  self.attribute_method_matchers += affixes.map! { |affix| AttributeMethodMatcher.new prefix: affix[:prefix], suffix: affix[:suffix] }
  undefine_attribute_methods
end
attribute_method_prefix(*prefixes) 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)
  self.attribute_method_matchers += prefixes.map! { |prefix| AttributeMethodMatcher.new prefix: prefix }
  undefine_attribute_methods
end
attribute_method_suffix(*suffixes) 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 142
def attribute_method_suffix(*suffixes)
  self.attribute_method_matchers += suffixes.map! { |suffix| AttributeMethodMatcher.new suffix: suffix }
  undefine_attribute_methods
end
define_attribute_method(attr_name) 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 283
def define_attribute_method(attr_name)
  attribute_method_matchers.each do |matcher|
    method_name = matcher.method_name(attr_name)

    unless instance_method_already_implemented?(method_name)
      generate_method = "define_method_#{matcher.target}"

      if respond_to?(generate_method, true)
        send(generate_method, attr_name.to_s)
      else
        define_proxy_call true, generated_attribute_methods, method_name, matcher.target, attr_name.to_s
      end
    end
  end
  attribute_method_matchers_cache.clear
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 250
def define_attribute_methods(*attr_names)
  attr_names.flatten.each { |attr_name| define_attribute_method(attr_name) }
end
undefine_attribute_methods() click to toggle source

Removes all the previously dynamically defined methods from the class.

class Person
  include ActiveModel::AttributeMethods

  attr_accessor :name
  attribute_method_suffix '_short?'
  define_attribute_method :name

  private

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

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

Person.undefine_attribute_methods

person.name_short? # => NoMethodError
# File lib/active_model/attribute_methods.rb, line 323
def undefine_attribute_methods
  generated_attribute_methods.module_eval do
    instance_methods.each { |m| undef_method(m) }
  end
  attribute_method_matchers_cache.clear
end

Private Instance Methods

attribute_method_matchers_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 348
def attribute_method_matchers_cache
  @attribute_method_matchers_cache ||= Concurrent::Map.new(initial_capacity: 4)
end
attribute_method_matchers_matching(method_name) click to toggle source
# File lib/active_model/attribute_methods.rb, line 352
def attribute_method_matchers_matching(method_name)
  attribute_method_matchers_cache.compute_if_absent(method_name) do
    # Bump plain matcher to last place so that only methods that do not
    # match any other pattern match the actual attribute name.
    # This is currently only needed to support legacy usage.
    matchers = attribute_method_matchers.partition(&:plain?).reverse.flatten(1)
    matchers.map { |matcher| matcher.match(method_name) }.compact
  end
end
define_proxy_call(include_private, mod, name, target, *extra) click to toggle source

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

# File lib/active_model/attribute_methods.rb, line 365
        def define_proxy_call(include_private, mod, name, target, *extra)
          defn = if NAME_COMPILABLE_REGEXP.match?(name)
            "def #{name}(*args)"
          else
            "define_method(:'#{name}') do |*args|"
          end

          extra = (extra.map!(&:inspect) << "*args").join(", ")

          body = if CALL_COMPILABLE_REGEXP.match?(target)
            "#{"self." unless include_private}#{target}(#{extra})"
          else
            "send(:'#{target}', #{extra})"
          end

          mod.module_eval <<-RUBY, __FILE__, __LINE__ + 1
            #{defn}
              #{body}
            end
            ruby2_keywords(:'#{name}') if respond_to?(:ruby2_keywords, true)
          RUBY
        end
generated_attribute_methods() click to toggle source
# File lib/active_model/attribute_methods.rb, line 331
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 335
def instance_method_already_implemented?(method_name)
  generated_attribute_methods.method_defined?(method_name)
end