require 'active_support/core_ext/hash/keys' require 'active_support/core_ext/class/inheritable_attributes' 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 # # Notice that whenever you include ActiveModel::AtributeMethods in your class, # it requires you to implement a attributes methods 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 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: # # AttributePerson.primary_key # # => "sysid" # AttributePerson.inheritance_column = 'address' # AttributePerson.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 # use eval instead of a block to work around a memory leak in dev # mode in fcgi sing.class_eval <<-eorb, __FILE__, __LINE__ + 1 def #{name}; #{value.to_s.inspect}; end eorb 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) attribute_method_matchers.concat(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) attribute_method_matchers.concat(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) attribute_method_matchers.concat(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| module_eval <<-STR, __FILE__, __LINE__ + 1 def #{matcher.method_name(new_name)}(*args) send(:#{matcher.method_name(old_name)}, *args) end STR end end # Declares a 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) return if attribute_methods_generated? attr_names.each do |attr_name| attribute_method_matchers.each do |matcher| unless instance_method_already_implemented?(matcher.method_name(attr_name)) generate_method = "define_method_#{matcher.prefix}attribute#{matcher.suffix}" if respond_to?(generate_method) send(generate_method, attr_name) else method_name = matcher.method_name(attr_name) generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__ + 1 if method_defined?(:#{method_name}) undef :#{method_name} end def #{method_name}(*args) send(:#{matcher.method_missing_target}, '#{attr_name}', *args) end STR end end end end @attribute_methods_generated = true end # Removes all the preiously 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_methods_generated = nil 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 # Returns true if the attribute methods defined have been generated. def attribute_methods_generated? @attribute_methods_generated ||= nil end protected def instance_method_already_implemented?(method_name) method_defined?(method_name) end private class AttributeMethodMatcher attr_reader :prefix, :suffix AttributeMethodMatch = Struct.new(:target, :attr_name) def initialize(options = {}) options.symbolize_keys! @prefix, @suffix = options[:prefix] || '', options[:suffix] || '' @regex = /^(#{Regexp.escape(@prefix)})(.+?)(#{Regexp.escape(@suffix)})$/ end def match(method_name) if matchdata = @regex.match(method_name) AttributeMethodMatch.new(method_missing_target, matchdata[2]) else nil end end def method_name(attr_name) "#{prefix}#{attr_name}#{suffix}" end def method_missing_target :"#{prefix}attribute#{suffix}" end end def attribute_method_matchers #:nodoc: read_inheritable_attribute(:attribute_method_matchers) || write_inheritable_attribute(:attribute_method_matchers, []) 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_id, *args, &block) method_name = method_id.to_s if match = match_attribute_method?(method_name) guard_private_attribute_method!(method_name, args) return __send__(match.target, match.attr_name, *args, &block) end super 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 return 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. return false elsif match_attribute_method?(method.to_s) return true end super 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) self.class.send(:attribute_method_matchers).each do |method| if (match = method.match(method_name)) && attribute_method?(match.attr_name) return match end end nil end # prevent method_missing from calling private methods with #send def guard_private_attribute_method!(method_name, args) if self.class.private_method_defined?(method_name) raise NoMethodError.new("Attempt to call private method", method_name, args) end end def missing_attribute(attr_name, stack) raise ActiveModel::MissingAttributeError, "missing attribute: #{attr_name}", stack end end end