require 'thread_safe' module ActiveModel # Raised when an attribute is not defined. # # class User < ActiveRecord::Base # has_many :pets # end # # user = User.first # user.pets.select(:id).first.user_id # # => ActiveModel::MissingAttributeError: missing attribute: user_id class MissingAttributeError < NoMethodError end # == Active \Model Attribute Methods # # ActiveModel::AttributeMethods provides a way to add prefixes and # suffixes to your methods as well as handling the creation of Active Record # like class methods such as +table_name+. # # The requirements to implement ActiveModel::AttributeMethods are to: # # * include ActiveModel::AttributeMethods in your object. # * Call each Attribute Method module method you want to add, such as # +attribute_method_suffix+ or +attribute_method_prefix+. # * Call +define_attribute_methods+ after the other methods are called. # * Define the various generic +_attribute+ methods that you have declared. # # A minimal implementation could be: # # class Person # include ActiveModel::AttributeMethods # # attribute_method_affix prefix: 'reset_', suffix: '_to_default!' # attribute_method_suffix '_contrived?' # attribute_method_prefix 'clear_' # define_attribute_methods :name # # attr_accessor :name # # private # # def attribute_contrived?(attr) # true # end # # def clear_attribute(attr) # send("#{attr}=", nil) # end # # def reset_attribute_to_default!(attr) # send("#{attr}=", 'Default Name') # end # end # # Note that whenever you include ActiveModel::AttributeMethods in your class, # it requires you to implement an +attributes+ method which returns a hash # with each attribute name in your model as hash key and the attribute value as # hash value. # # Hash keys must be strings. module AttributeMethods extend ActiveSupport::Concern NAME_COMPILABLE_REGEXP = /\A[a-zA-Z_]\w*[!?=]?\z/ CALL_COMPILABLE_REGEXP = /\A[a-zA-Z_]\w*[!?]?\z/ included do class_attribute :attribute_aliases, :attribute_method_matchers, instance_writer: false self.attribute_aliases = {} self.attribute_method_matchers = [ClassMethods::AttributeMethodMatcher.new] end module ClassMethods # 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 def attribute_method_prefix(*prefixes) self.attribute_method_matchers += prefixes.map! { |prefix| AttributeMethodMatcher.new prefix: prefix } undefine_attribute_methods end # 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 def attribute_method_suffix(*suffixes) self.attribute_method_matchers += suffixes.map! { |suffix| AttributeMethodMatcher.new suffix: suffix } undefine_attribute_methods end # 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) # ... # end # end # # person = Person.new # person.name # => 'Gem' # person.reset_name_to_default! # person.name # => 'Gemma' def attribute_method_affix(*affixes) self.attribute_method_matchers += affixes.map! { |affix| AttributeMethodMatcher.new prefix: affix[:prefix], suffix: affix[:suffix] } undefine_attribute_methods end # 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 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 # 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 declares. # define_attribute_methods :name, :age, :address # # private # # def clear_attribute(attr) # ... # end # end def define_attribute_methods(*attr_names) attr_names.flatten.each { |attr_name| define_attribute_method(attr_name) } end # 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 declares. # 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 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.method_missing_target}" if respond_to?(generate_method, true) send(generate_method, attr_name) else define_proxy_call true, generated_attribute_methods, method_name, matcher.method_missing_target, attr_name.to_s end end end attribute_method_matchers_cache.clear end # 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 def undefine_attribute_methods generated_attribute_methods.module_eval do instance_methods.each { |m| undef_method(m) } end attribute_method_matchers_cache.clear end # Returns true if the attribute methods defined have been generated. def generated_attribute_methods #:nodoc: @generated_attribute_methods ||= Module.new.tap { |mod| include mod } end protected def instance_method_already_implemented?(method_name) #:nodoc: generated_attribute_methods.method_defined?(method_name) end private # The methods +method_missing+ and +respond_to?+ of this module are # invoked often in a typical rails, both of which invoke the method # +match_attribute_method?+. The latter method iterates through an # array doing regular expression matches, which results in a lot of # object creations. Most of the times 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). def attribute_method_matchers_cache #:nodoc: @attribute_method_matchers_cache ||= ThreadSafe::Cache.new(:initial_capacity => 4) end def attribute_method_matcher(method_name) #:nodoc: attribute_method_matchers_cache.compute_if_absent(method_name) do # Must try to match prefixes/suffixes first, or else the matcher with no prefix/suffix # will match every time. matchers = attribute_method_matchers.partition(&:plain?).reverse.flatten(1) match = nil matchers.detect { |method| match = method.match(method_name) } match end end # Define a method `name` in `mod` that dispatches to `send` # using the given `extra` args. This fallbacks `define_method` # and `send` if the given names cannot be compiled. def define_proxy_call(include_private, mod, name, send, *extra) #:nodoc: defn = if name =~ NAME_COMPILABLE_REGEXP "def #{name}(*args)" else "define_method(:'#{name}') do |*args|" end extra = (extra.map!(&:inspect) << "*args").join(", ") target = if send =~ CALL_COMPILABLE_REGEXP "#{"self." unless include_private}#{send}(#{extra})" else "send(:'#{send}', #{extra})" end mod.module_eval <<-RUBY, __FILE__, __LINE__ + 1 #{defn} #{target} end RUBY end class AttributeMethodMatcher #:nodoc: attr_reader :prefix, :suffix, :method_missing_target AttributeMethodMatch = Struct.new(:target, :attr_name, :method_name) def initialize(options = {}) if options[:prefix] == '' || options[:suffix] == '' message = "Specifying an empty prefix/suffix for an attribute method is no longer " \ "necessary. If the un-prefixed/suffixed version of the method has not been " \ "defined when `define_attribute_methods` is called, it will be defined " \ "automatically." ActiveSupport::Deprecation.warn message end @prefix, @suffix = options.fetch(:prefix, ''), options.fetch(:suffix, '') @regex = /^(?:#{Regexp.escape(@prefix)})(.*)(?:#{Regexp.escape(@suffix)})$/ @method_missing_target = "#{@prefix}attribute#{@suffix}" @method_name = "#{prefix}%s#{suffix}" end def match(method_name) if @regex =~ method_name AttributeMethodMatch.new(method_missing_target, $1, method_name) end end def method_name(attr_name) @method_name % attr_name end def plain? prefix.empty? && suffix.empty? end end end # Allows access to the object attributes, which are held in the # @attributes hash, as though they were first-class methods. So a # Person class with a name attribute can use Person#name and Person#name= # and never directly use the attributes hash -- except for multiple assigns # with ActiveRecord#attributes=. A Milestone class can also ask # Milestone#completed? to test that the completed attribute is not +nil+ # or 0. # # It's also possible to instantiate related objects, so a Client class # belonging to the clients table with a +master_id+ foreign key can # instantiate master through Client#master. def method_missing(method, *args, &block) if respond_to_without_attributes?(method, true) super else match = match_attribute_method?(method.to_s) match ? attribute_missing(match, *args, &block) : super end end # attribute_missing is like method_missing, but for attributes. When method_missing is # called we check to see if there is a matching attribute method. If so, we call # attribute_missing to dispatch the attribute. This method can be overloaded to # customize the behavior. def attribute_missing(match, *args, &block) __send__(match.target, match.attr_name, *args, &block) end # 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+. alias :respond_to_without_attributes? :respond_to? def respond_to?(method, include_private_methods = false) if super true elsif !include_private_methods && super(method, true) # If we're here then we haven't found among non-private methods # but found among all methods. Which means that the given method is private. false else !match_attribute_method?(method.to_s).nil? end end protected def attribute_method?(attr_name) #:nodoc: respond_to_without_attributes?(:attributes) && attributes.include?(attr_name) end private # Returns a struct representing the matching attribute method. # The struct's attributes are prefix, base and suffix. def match_attribute_method?(method_name) match = self.class.send(:attribute_method_matcher, method_name) match if match && attribute_method?(match.attr_name) end def missing_attribute(attr_name, stack) raise ActiveModel::MissingAttributeError, "missing attribute: #{attr_name}", stack end end end