GuerillaPatch is a Ruby gem to ease the transition to Ruby 2.0 when redefining behavior in existing objects (monkey patching). Ruby 2.0 introduces a new feature called refinements which allows you to create monkey patches that only exist in a scope where the refinement is explicitly included, preventing your changes from affected code that has not opted in.

Using GuerillaPatch, you can use a common interface for writing a monkey patch that will use refinements if available, working seemlessly for both Ruby 1.9 and Ruby 2.0.


Add this line to your application's Gemfile:

gem 'guerilla_patch'

And then execute:

$ bundle

Or install it yourself with:

$ gem install guerilla_patch


To create a new monkey patch, use GuerillaPatch.patch. The first argument is the object you are patching, and the second argument is the name to use for the refinement if run under Ruby 2.0. Pass a block with the methods you want to add to the object, or any other modifications you want to make.

GuerillaPatch.patch(Fixnum, "TimeExtensions") do
  def minutes
    self * 60

Then, in Ruby 1.9:

2.minutes # => 120

And in Ruby 2.0:

class MyApp
  using TimeExtensions

  def minutes_to_seconds(m)
end # => 120