Refinement is introduced in ruby 2.0, no longer a experiment feature in ruby 2.1, but still not very stable. The idea of refinement is to limit the monkeying patch scope.

For example, suppose we define a refinement:

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module ACoolFeature
  refine(String) do
    def is_it_cool?
      puts "YES"
    end
  end
end

Here we define a refinement to String class, to use the refinement we need to call using inside a class.

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class Person
  using(ACoolFeature)

  def hello
    "test".is_it_cool?
  end
end

After call using in Person class, the method is_it_cool? is available for string inside this scope.

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Person.new.hello
>     Person.new.hello
YES

That’s it.