class Surrogate # Adds surrogate behaviour to your class / singleton class / instances # # please refactor me! class Endower def self.endow(klass, &playlist) new(klass, &playlist).endow end attr_accessor :klass, :playlist def initialize(klass, &playlist) self.klass, self.playlist = klass, playlist end def endow endow_klass endow_singleton_class end private def endow_klass add_hatchery_to klass klass.extend ClassMethods enable_defining_methods klass record_initialization_for_instances_of klass remember_invocations_for_instances_of klass remember_invocations_for_instances_of klass.singleton_class end def endow_singleton_class hatchery = add_hatchery_to singleton enable_defining_methods singleton singleton.module_eval &playlist if playlist klass.instance_variable_set :@hatchling, Hatchling.new(klass, hatchery) klass end # yeesh :( pretty sure there isn't a better way to do this def record_initialization_for_instances_of(klass) def klass.method_added(meth) return if meth != :initialize || @hijacking_initialize @hijacking_initialize = true current_initialize = instance_method :initialize # `define' records the args while maintaining the old behaviour # we have to do it stupidly like this because there is no to_proc on an unbound method define :initialize do |*args, &block| current_initialize.bind(self).call(*args, &block) end ensure @hijacking_initialize = false end initialize = klass.instance_method :initialize klass.send :define_method, :initialize do |*args, &block| initialize.bind(self).call(*args, &block) end end def singleton klass.singleton_class end def remember_invocations_for_instances_of(klass) klass.send :define_method, :invocations do |method_name| @hatchling.invocations method_name end end def add_hatchery_to(klass) klass.instance_variable_set :@hatchery, Surrogate::Hatchery.new(klass) end def enable_defining_methods(klass) def klass.define(method_name, options={}, &block) @hatchery.define method_name, options, block end def klass.api_method_names @hatchery.api_method_names end end end # use a module so that the method is inherited (important for substitutability) module ClassMethods def clone hatchling, hatchery = @hatchling, @hatchery Class.new self do Surrogate.endow self do hatchling.api_methods.each { |name, options| define name, options.to_hash, &options.default_proc } end hatchery.api_methods.each { |name, options| define name, options.to_hash, &options.default_proc } end end # Custom new, because user can define initialize, and ivars should be set before it def new(*args) instance = allocate instance.instance_variable_set :@hatchling, Hatchling.new(instance, @hatchery) instance.send :initialize, *args instance end end end