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Unleash the Secrets of the Standard Library with SimpleDelegator, Forwardable, and more Monday, November 11, 13

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Jim Gay @saturnflyer Monday, November 11, 13

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standard library vs. standard library Monday, November 11, 13

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Monday, November 11, 13

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Monday, November 11, 13

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require ‘delegate’ Monday, November 11, 13

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user Monday, November 11, 13

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born user Monday, November 11, 13

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born user #

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born user 1989 Monday, November 11, 13

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user 1989 decorator born Monday, November 11, 13

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born user 1989 decorator born # Monday, November 11, 13

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born user decorator born year # 1989 Monday, November 11, 13

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Delegator SimpleDelegator DelegateClass() Monday, November 11, 13

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class D;def initialize(o);@o=o;end;def method_missing(m, *r, &b);@o.send(m,*r,&b);end;end Monday, November 11, 13

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class D def initialize(o) @o = o end def method_missing(m, *r, &b) @o(m, *r, &b) end end Monday, November 11, 13

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class Delegator def initialize(object) @object = object end def method_missing(method, *args, &block) @object.send(method, *args, &block) end end Monday, November 11, 13

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class Delegator def initialize(object) @object = object end def method_missing(method, *args, &block) @object.send(method, *args, &block) end end Monday, November 11, 13

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class Delegator def initialize(object) @object = object end def method_missing(method, *args, &block) @object.send(method, *args, &block) end end Monday, November 11, 13

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class User def born Date.new(1989, 9, 10) end end user = User.new Monday, November 11, 13

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class User def born Date.new(1989, 9, 10) end def birth_year born.year end end user = User.new user.birth_year #=> 1989 Monday, November 11, 13

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class User def born Date.new(1989, 9, 10) end end class UserDecorator < Delegator def born super.year end end user = User.new decorated_user = UserDecorator.new(user) decorated_user.born #=> 1989 Monday, November 11, 13

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user = User.new decorated_user = UserDecorator.new(user) decorated_user.born == user.born.year #=> true Monday, November 11, 13

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user = User.new decorated_user = UserDecorator.new(user) decorated_user.born == user.born.year #=> true decorated_user == user #=> ???? Monday, November 11, 13

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user = User.new decorated_user = UserDecorator.new(user) decorated_user.born == user.born.year #=> true decorated_user == user #=> false Monday, November 11, 13

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class UserDecorator < Delegator def born super.year end def ==(other) @object == other end end decorated_user == user #=> true Monday, November 11, 13

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class UserDecorator < Delegator def born super.year end def ==(other) @object == other end end decorated_user == user #=> true decorated_user == decorated_user #=> ???? Monday, November 11, 13

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class UserDecorator < Delegator def born super.year end def ==(other) @object == other end end decorated_user == user #=> true decorated_user == decorated_user #=> false Monday, November 11, 13

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class UserDecorator < Delegator def born super.year end def ==(other) return true if other.equal?(self) @object == other end end decorated_user == user #=> true decorated_user == decorated_user #=> true Monday, November 11, 13

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require 'delegate' class UserDecorator < SimpleDelegator def born super.year end end decorated_user == user #=> true decorated_user == decorated_user #=> true Monday, November 11, 13

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class SimpleDelegator < Delegator end class Delegator < BasicObject def initialize(obj) __setobj__(obj) end def method_missing(m, *args, &block) self.__getobj__.send(m, *args, &block) end def __getobj__ raise NotImplementedError, "need to define `__getobj__'" end def __setobj__(obj) raise NotImplementedError, "need to define `__setobj__'" end end Monday, November 11, 13

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class SimpleDelegator < Delegator def __getobj__ @delegate_sd_obj end def __setobj__(obj) raise ArgumentError, "cannot delegate to self" if self.equal?(obj) @delegate_sd_obj = obj end end Monday, November 11, 13

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class SimpleDelegator < Delegator def __getobj__ @delegate_sd_obj end def __setobj__(obj) raise ArgumentError, "cannot delegate to self" if self.equal?(obj) @delegate_sd_obj = obj end end Monday, November 11, 13

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require 'delegate' class UserDec < Delegator def __setobj__(obj) @obj = obj end def __getobj__ @obj end end require 'delegate' class UserDec < SimpleDelegator end Monday, November 11, 13

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require 'delegate' class UserDec < Delegator def __setobj__(obj) @obj = obj end def __getobj__ @obj end end require 'delegate' class UserDec < SimpleDelegator end SystemStackError: stack level too deep Monday, November 11, 13

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require 'delegate' class UserDec < Delegator def __setobj__(obj) @obj = obj end def __getobj__ @obj end end require 'delegate' class UserDec < SimpleDelegator end problem solved Monday, November 11, 13

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UserDecorator #=> __getobj__, __setobj__ ProfileDecorator #=> __getobj__, __setobj__ ShoppingCartDecorator #=> __getobj__, __setobj__ Monday, November 11, 13

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UserDecorator #=> user, user= ProfileDecorator #=> profile, profile= ShoppingCartDecorator #=> shopping_cart, shopping_cart= Monday, November 11, 13

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class UserDecorator < Decorator alias_method :user, :__getobj__ alias_method :user=, :__setobj__ end Monday, November 11, 13

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class UserDecorator < Decorator alias_method :user, :__getobj__ alias_method :user=, :__setobj__ end class ProfileDecorator < Decorator alias_method :profile, :__getobj__ alias_method :profile=, :__setobj__ end Monday, November 11, 13

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class UserDecorator < Decorator alias_method :user, :__getobj__ alias_method :user=, :__setobj__ end class ProfileDecorator < Decorator alias_method :profile, :__getobj__ alias_method :profile=, :__setobj__ end class ShoppingCartDecorator < Decorator alias_method :shopping_cart, :__getobj__ alias_method :shopping_cart=, :__setobj__ end Monday, November 11, 13

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class Decorator < SimpleDelegator def self.inherited(klass) # get the part of the class name # we want like "ShoppingCart" base_name = klass.name.split('::').last.sub('Decorator','') # downcase and underscore # (without activesupport) like "shopping_cart" object_name = base_name.gsub(/([a-z][A-Z])/){ $1.scan(/./).join('_') }.downcase klass.send(:alias_method, object_name, :__getobj__) klass.send(:alias_method, "#{object_name}=", :__setobj__) end end Monday, November 11, 13

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class Decorator < SimpleDelegator def self.inherited(klass) # get the part of the class name # we want like "ShoppingCart" base_name = klass.name.split('::').last.sub('Decorator','') # downcase and underscore # (without activesupport) like "shopping_cart" object_name = base_name.gsub(/([a-z][A-Z])/){ $1.scan(/./).join('_') }.downcase klass.send(:alias_method, object_name, :__getobj__) klass.send(:alias_method, "#{object_name}=", :__setobj__) end end Monday, November 11, 13

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class Decorator < SimpleDelegator def self.inherited(klass) # get the part of the class name # we want like "ShoppingCart" base_name = klass.name.split('::').last.sub('Decorator','') # downcase and underscore # (without activesupport) like "shopping_cart" object_name = base_name.gsub(/([a-z][A-Z])/){ $1.scan(/./).join('_') }.downcase klass.send(:alias_method, object_name, :__getobj__) klass.send(:alias_method, "#{object_name}=", :__setobj__) end end Monday, November 11, 13

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class Decorator < SimpleDelegator def self.inherited(klass) # get the part of the class name # we want like "ShoppingCart" base_name = klass.name.split('::').last.sub('Decorator','') # downcase and underscore # (without activesupport) like "shopping_cart" object_name = base_name.gsub(/([a-z][A-Z])/){ $1.scan(/./).join('_') }.downcase klass.send(:alias_method, object_name, :__getobj__) klass.send(:alias_method, "#{object_name}=", :__setobj__) end end Monday, November 11, 13

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class Decorator < SimpleDelegator def self.inherited(klass) # get the part of the class name # we want like "ShoppingCart" base_name = klass.name.split('::').last.sub('Decorator','') # downcase and underscore # (without activesupport) like "shopping_cart" object_name = base_name.gsub(/([a-z][A-Z])/){ $1.scan(/./).join('_') }.downcase klass.send(:alias_method, object_name, :__getobj__) klass.send(:alias_method, "#{object_name}=", :__setobj__) end end Monday, November 11, 13

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UserDecorator #=> user, user= ProfileDecorator #=> profile, profile= ShoppingCartDecorator #=> shopping_cart, shopping_cart= Monday, November 11, 13

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class Delegator < BasicObject kernel = ::Kernel.dup kernel.class_eval do [:to_s,:inspect,:=~,:!~,:===,:<=>,:eql?,:hash].each do |m| undef_method m end end include kernel #... end Monday, November 11, 13

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class Delegator < BasicObject kernel = ::Kernel.dup kernel.class_eval do [:to_s,:inspect,:=~,:!~,:===,:<=>,:eql?,:hash].each do |m| undef_method m end end include kernel #... end BasicObject.ancestors #=> [BasicObject] Object.ancestors # => [Object, Kernel, BasicObject] Monday, November 11, 13

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user.inspect #=> "#" user.to_s #=> "#" Monday, November 11, 13

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user.inspect #=> "#" user.to_s #=> "#" decorated_user.inspect #=> "#" decorated_user.to_s #=> "#" Monday, November 11, 13

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user.inspect #=> "#" user.to_s #=> "#" decorated_user.inspect #=> "#" decorated_user.to_s #=> "#" user.class #=> User decorated_user.class #=> UserDecorator Monday, November 11, 13

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decorated_user.class #=> UserDecorator <%= form_for(decorated_user) do |f| %> Monday, November 11, 13

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# https://github.com/objects-on-rails/display-case module DisplayCase class Exhibit < SimpleDelegator alias_method :__class__, :class def class __getobj__.class end end end Monday, November 11, 13

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# https://github.com/drapergem/draper module Draper class Decorator def self.object_class @object_class ||= inferred_object_class end def self.inferred_object_class name = object_class_name name.constantize rescue NameError => error raise if name && !error.missing_name?(name) raise Draper::UninferrableSourceError.new(self) end # ActiveModel compatibility singleton_class.delegate :model_name, to: :object_class end end Monday, November 11, 13

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decorated_user.class #=> UserDecorator <%= form_for(decorated_user) do |f| %> Monday, November 11, 13

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decorated_user.class #=> UserDecorator <%= form_for(decorated_user) do |f| %> Monday, November 11, 13

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def DelegateClass(superclass) klass = Class.new(Delegator) methods = superclass.instance_methods methods -= ::Delegator.public_api methods -= [:to_s,:inspect,:=~,:!~,:===] klass.module_eval do def __getobj__ # :nodoc: @delegate_dc_obj end def __setobj__(obj) # :nodoc: raise ArgumentError, "cannot delegate to self" if self.equal?(o @delegate_dc_obj = obj end methods.each do |method| define_method(method, Delegator.delegating_block(method)) end end klass.define_singleton_method :public_instance_methods do |all=true super(all) - superclass.protected_instance_methods end klass.define_singleton_method :protected_instance_methods do |all=t super(all) | superclass.protected_instance_methods end return klass end Monday, November 11, 13

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def DelegateClass(superclass) klass = Class.new(Delegator) # lots of code... return klass end Monday, November 11, 13

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class UserDecorator < Decorator end UserDecorator.ancestors #=> [UserDecorator, Decorator, SimpleDelegator, Delegator, #, BasicObject] class Decorator < SimpleDelegator end Monday, November 11, 13

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class UserDecorator < DelegateClass(User) alias_method :user, :__getobj__ alias_method :user=, :__setobj__ end UserDecorator.ancestors #=> [UserDecorator, #, Delegator, #, BasicObject] Monday, November 11, 13

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UserDecorator = Class.new(DelegateClass(user.class)) do base_name = user.class.name.split('::').last object_name = base_name.gsub(/([a-z][A-Z])/){ $1.scan(/./).join('_') }.downcase self.send(:alias_method, object_name, :__getobj__) self.send(:alias_method, "#{object_name}=", :__setobj__) end UserDecorator.ancestors #=> [UserDecorator, #, Delegator, #, BasicObject] Monday, November 11, 13

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gem install 'decoratificationizer' def DecoratificationClass(obj) Class.new(DelegateClass(obj.class)) do base_name = obj.class.name.split('::').last object_name = base_name.gsub(/([a-z][A-Z])/){ $1.scan(/./).join('_') }.downcase self.send(:alias_method, object_name, :__getobj__) self.send(:alias_method, "#{object_name}=", :__setobj__) end end klass = DecoratificationClass(user) Monday, November 11, 13

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require ‘forwardable’ Monday, November 11, 13

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user addr. address Monday, November 11, 13

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user addr. address city Miami Monday, November 11, 13

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user city Miami Monday, November 11, 13

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user city address city Miami Monday, November 11, 13

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Forwardable SingleForwardable Monday, November 11, 13

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module Fwd;def fwd(a,m,n=m);self.class_eval"def #{n} (*r,&b);#{a}.__send__(:#{m},*r,&b);end";end;end Monday, November 11, 13

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module Fwd def fwd(a,m,n=m) self.class_eval " def #{n}(*r,&b) #{a}.__send__(:#{m},*r,&b) end " end end Monday, November 11, 13

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module Forward def forward(to, method_name, alternative=method_name) self.class_eval " def #{alternative}(*args, &block) #{to}.__send__(:#{method_name},*args, &block) end " end end Monday, November 11, 13

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class Address attr_accessor :number, :street, :city, :province, :postal_code end class Person attr_accessor :name, :address end home = Address.new.tap{|address| address.number = "123" address.street = "Main Street" address.city = "Miami" address.province = "FL" address.postal_code = "12345" } jim = Person.new jim.name = "Jim" jim.address = home Monday, November 11, 13

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# Which city? jim.address.city #=> "Miami" class Person def city address.city end end jim.city #=> "Miami" Monday, November 11, 13

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# Which city? jim.address.city #=> "Miami" class Person extend Forward forward :address, :city end jim.city #=> "Miami" Monday, November 11, 13

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# Which city? jim.address.city #=> "Miami" class Person extend Forward forward :address, :city, :home_city end jim.city #=> NoMethodError jim.home_city #=> "Miami" Monday, November 11, 13

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# Which city? jim.address.city #=> "Miami" class Person extend Forward forward :address, :city, :home_city forward :address, :number, :home_number forward :address, :postal_code, :home_postal_code end Monday, November 11, 13

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require 'forwardable' class Person extend Forwardable def_delegator :address, :city, :home_city def_delegator :address, :number, :home_number def_delegator :address, :postal_code, :home_postal_code end Monday, November 11, 13

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require 'forwardable' class Person extend Forwardable def_delegator :address, :city def_delegator :address, :number def_delegator :address, :postal_code end Monday, November 11, 13

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require 'forwardable' class Person extend Forwardable def_delegators :address, :city, :number, :postal_code end Monday, November 11, 13

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require 'forwardable' class Person extend Forwardable delegate [:city, :number, :postal_code] => :address end Monday, November 11, 13

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require 'forwardable' class Person extend Forwardable delegate [:city, :number, :postal_code] => :@address end Monday, November 11, 13

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# With ActiveSupport class Person delegate :city, :number, :postal_code, :to => :address, :allow_nil => true, :prefix => true end person.address_city #=> "Miami" Monday, November 11, 13

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# With ActiveSupport class Person delegate :city, :number, :postal_code, :to => :address, :allow_nil => true, :prefix => 'home_' end person.home_city #=> "Miami" Monday, November 11, 13

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def oops! fail rescue IveMadeAHugeMistake => e Airbrake.notify(e) end Monday, November 11, 13

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def oops! fail rescue IveMadeAHugeMistake => e Catcher.save_for_later(e) # Build your own Facade end Monday, November 11, 13

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require 'forwardable' module Catcher extend SingleForwardable def_delegator :AppSignal, :send_exception, :save_for_later # def_delegator :Airbrake, :notify, :save_for_later end Catcher.save_for_later(exception) Monday, November 11, 13

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object decorator SimpleDelegator object related Forwardable run time behavior load time behavior Monday, November 11, 13

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Extra credit at github.com... saturnflyer/casting myobie/rep stevenharman/dumb_delegator elight/modest_presenter Monday, November 11, 13

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clean-ruby.com RUBYCONF 20% off @saturnflyer Thanks! Monday, November 11, 13