PORO decorators with SimpleDelegator

19 Jan 2015 |

An easy and PORO way to create decorators is using ruby’s SimpleDelegator.

SimpleDelegator

A concrete implementation of Delegator, this class provides the means to delegate all supported method calls to the object passed into the constructor and even to change the object being delegated to at a later time with #__setobj__.

I like the decorators to behave like they are the class that’s been decorated. To acheive this let’s create a class Decorator which inherits from SimpleDelegator.

class Decorator < SimpleDelegator
  def component
    @component ||= __getobj__
  end

  def class
    component.class
  end
end

As you can see we created the method component which will return the object it’s decorating and the method class which will return the component class.

Now let’s create a UserDecorator that inherits from Decorator.

class UserDecorator < Decorator
  def pirate_name
    "Ahoy! #{first_name}"
  end
end

Great! But how do we use this decorator?

decorated_user = UserDecorator.new(current_user)
decorated_user.pirate_name # => Ahoy! Adrian

So decorating objects allows you to avoid having view logic on your model.