TypeWrapper

Delegator pattern in Ruby without object schizophrenia. Because Object#extend at runtime is evil.

Installation

Add this line to your application's Gemfile:

gem 'type_wrapper'

And then execute:

$ bundle

Or install it yourself as:

$ gem install type_wrapper

Usage

TypeWrapper

Construct a delegator class using square brackets '[]' method with type as the first argument followed by mixins.

module ToArray
  def to_a
    [self]
  end
end

module ToString
  def to_s
    "#{self}"
  end
end

Person = Struct.new(:name)

PersonPresenter = TypeWrapper[Person, ToArray, ToString]

peter = PersonPresenter.new(Person.new('Peter'))
peter.to_a

TypeWrapper::Module

Define a block with the 'new' method and pass the 'mod' parameter to 'using' keyword.

AwesomeSinging = TypeWrapper::Module.new do |mod| using mod
  def sing
    "#{name} sings #{song}"
  end

  def song
    "Everything is AWESOME!!!"
  end
end

Lego = Struct.new(:name)

using AwesomeSinging[Lego]
Lego.new("Emmet").sing

TypeWrapper::Forwarding

Creates a Module that delegates Refinements methods (forwarding) to a target object.

Lego = Struct.new(:name)

module LoudSpeaking
  def speak(words)
    "#{name}: #{words.upcase}!!!"
  end

  def say(words)
    "#{name}: #{words.upcase}!!!"
  end
end

# Refinements
module LoudSpeakingLego
  refine Lego do
    include LoudSpeaking
  end
end

# target: speaker
class LoudLego < Struct.new(:speaker)
  include TypeWrapper::Forwarding[LoudSpeakingLego, :speak, :say, to: :speaker]
end

batman = Lego.new('Batman')
loud_lego = LoudLego.new(batman)
loud_lego.speak("I'm Batman") # => "Batman: I'M BATMAN!!!"

Pros

• Five (5) times faster than Object#extend.
• Delegation without self schizophrenia.
• Decorator Pattern with multiple traits.
• Allows DCI in Ruby without blowing the method cache at run time.

Cons

• Must use TypeWrapper::Module to allow procedural code in mixins.
• Three (3) times slower than calling class method. See benchmark.
• Methods applied with Object#extend takes precedence over Mixin methods.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/RichOrElse/type_wrapper.

License

The gem is available as open source under the terms of the MIT License.