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Gem Version build status coverage report

Rint (Ruby Interface)

Rint provides a way to implement behaviour defined by Interface files, warning when the desired behaviour is missing.


require 'interface'
module Playable
  include Interface

  def initialize
    must_implement :play, play_quietly: 1

class Instrument
  implements Playable
end # will throw: Interface::Error::NotImplementedError: Expected Instrument to implement play for interface Playable

As showed in the example above,must_implement allows you enforce the implementation of the methods, specifying the arity. When not specified, only the method implementation will be checked.

There is also a CLI to generate the interfaces from the command line:

$ rint c Playable play play_quietly:1

will generate lib/playable.rb (namespaces are also supported).


Add it to your Gemfile:

gem 'rint'

and run

$ bundle install


Duck typing can be evil if not used correctly. While Ruby applications can get a good level of confidence about issues arisen by duck typing, the fear of a method missing exception or constant changes to a class may lead the developer to use safety checks such as respond_to? or raise Errors when a method is missing.

This implementation of rint wraps what other static languages use and encapsulates the safety check in a common place, also making explicit the behaviour through the word "implements" and expecting the developer to guess the behaviour of a class without looking at docs or partially implemented code.

It also provides a centralised way to implement the interface pattern without having the code throwing an error in a hidden method.


The environment variable DISABLE_RUBY_INTERFACE can be set to 1 in order to globally disable the interfaces - no Error will get thrown. This might be particularly useful in production for performance reasons if we are confident enough through tests that the interfaces are all implemented.


  • Fork it

  • Create your feature branch (git checkout -b my-new-feature)

  • Commit your changes (git commit -am 'Add some feature')

  • Push to the branch (git push origin my-new-feature)

  • Create new Pull Request

  • Enjoy!



Free Software, Hell Yeah!

Copyright 2015 James Lopez

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