require 'active_support/core_ext/hash/keys' require 'active_support/core_ext/class/attribute' require 'active_support/deprecation' module ActiveModel 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_method_matchers, :instance_writer => false self.attribute_method_matchers = [ClassMethods::AttributeMethodMatcher.new] end module ClassMethods # Defines an "attribute" method (like +inheritance_column+ or +table_name+). # A new (class) method will be created with the given name. If a value is # specified, the new method will return that value (as a string). # Otherwise, the given block will be used to compute the value of the # method. # # The original method will be aliased, with the new name being prefixed # with "original_". This allows the new method to access the original # value. # # Example: # # class Person # # include ActiveModel::AttributeMethods # # cattr_accessor :primary_key # cattr_accessor :inheritance_column # # define_attr_method :primary_key, "sysid" # define_attr_method( :inheritance_column ) do # original_inheritance_column + "_id" # end # # end # # Provides you with: # # Person.primary_key # # => "sysid" # Person.inheritance_column = 'address' # Person.inheritance_column # # => 'address_id' def define_attr_method(name, value=nil, &block) sing = singleton_class sing.class_eval <<-eorb, __FILE__, __LINE__ + 1 if method_defined?('original_#{name}') undef :'original_#{name}' end alias_method :'original_#{name}', :'#{name}' eorb if block_given? sing.send :define_method, name, &block else # If we can compile the method name, do it. Otherwise use define_method. # This is an important *optimization*, please don't change it. define_method # has slower dispatch and consumes more memory. if name =~ NAME_COMPILABLE_REGEXP sing.class_eval <<-RUBY, __FILE__, __LINE__ + 1 def #{name}; #{value.nil? ? 'nil' : value.to_s.inspect}; end RUBY else value = value.to_s if value sing.send(:define_method, name) { value } end end end # 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. # # For example: # # 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. # # For example: # # 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. # # For example: # # 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 def alias_attribute(new_name, old_name) 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_optimized_call self, matcher_new, matcher_old end end # Declares the attributes that should be prefixed and suffixed by # ActiveModel::AttributeMethods. # # To use, pass in an array of 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.each { |attr_name| define_attribute_method(attr_name) } end 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) send(generate_method, attr_name) else define_optimized_call 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 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 ||= begin mod = Module.new include mod mod end end protected def instance_method_already_implemented?(method_name) 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 ||= {} end def attribute_method_matcher(method_name) #:nodoc: if attribute_method_matchers_cache.key?(method_name) attribute_method_matchers_cache[method_name] else # 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) } attribute_method_matchers_cache[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_optimized_call(mod, name, send, *extra) #:nodoc: if name =~ NAME_COMPILABLE_REGEXP defn = "def #{name}(*args)" else defn = "define_method(:'#{name}') do |*args|" end extra = (extra.map(&:inspect) << "*args").join(", ") if send =~ CALL_COMPILABLE_REGEXP target = "#{send}(#{extra})" else target = "send(:'#{send}', #{extra})" end mod.module_eval <<-RUBY, __FILE__, __LINE__ + 1 #{defn} #{target} end RUBY end class AttributeMethodMatcher attr_reader :prefix, :suffix, :method_missing_target AttributeMethodMatch = Struct.new(:target, :attr_name, :method_name) def initialize(options = {}) options.symbolize_keys! if options[:prefix] == '' || options[:suffix] == '' ActiveSupport::Deprecation.warn( "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." ) end @prefix, @suffix = options[:prefix] || '', options[: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, $2, method_name) else nil 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 # customise the behaviour. 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) 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 && attribute_method?(match.attr_name) ? match : nil end def missing_attribute(attr_name, stack) raise ActiveModel::MissingAttributeError, "missing attribute: #{attr_name}", stack end end end