DumbDelegator

Build Status Dependency Status

Ruby provides the delegate standard library. However, we found that it is not appropriate for many use cases that require nearly every call to be proxied.

For instance, Rails uses #class and #instance_of? to introspect on model classes when generating forms and URL helpers. These methods are not forwarded when using Delegator or SimpleDelegator.

require 'delegate'

class MyAwesomeClass
  # ...
end

o = MyAwesomeClass.new
d = SimpleDelegator.new(o)

d.class                # => SimpleDelegator
d.is_a? MyAwesomeClass # => false

DumbDelegator, on the other hand, forwards almost ALL the things:

require 'dumb_delegator'

class MyAwesomeClass
  # ...
end

o = MyAwesomeClass.new
d = DumbDelegator.new(o)

d.class                # => MyAwesomeClass
d.is_a? MyAwesomeClass # => true

Usage

Rails Model Decorator

There are many decorator implementations in Ruby. One of the simplest is "SimpleDelegator + super + getobj," but it has the drawback of confusing Rails. It is necessary to redefine class. We've also observed the need to redefine instance_of? for URL helpers.

With DumbDelegator, there's not a need for this hackery because nearly every possible method is delegated:

require 'dumb_delegator'

class Coffee
  def cost
    2
  end

  def origin
    "Colombia"
  end
end

class Milk < DumbDelegator
  def cost
    super + 0.4
  end
end

class Sugar < DumbDelegator
  def cost
    super + 0.2
  end
end

coffee = Coffee.new
Sugar.new(Milk.new(coffee)).cost   # 2.6
Sugar.new(Sugar.new(coffee)).cost  # 2.4
Milk.new(coffee).origin            # Colombia
Sugar.new(Milk.new(coffee)).class  # Coffee

Installation

Add this line to your application's Gemfile:

gem 'dumb_delegator'

And then execute:

$ bundle

Or install it yourself as:

$ gem install dumb_delegator

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Added some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

Contribution Ideas/Needs

  1. Ruby 1.8 support (use the blankslate gem?)