How to refine module method in Ruby?

Question

You can refine your class with

module RefinedString
  refine String do
    def to_boolean(text)
    !!(text =~ /^(true|t|yes|y|1)$/i)
    end
  end
end

but how to refine module method? This:

module RefinedMath
  refine Math do
    def PI
      22/7
    end
  end
end

raises: TypeError: wrong argument type Module (expected Class)

Answer 1

This piece of code will work:

module Math
  def self.pi
    puts 'original method'
   end
end

module RefinementsInside
  refine Math.singleton_class do
    def pi
      puts 'refined method'
    end
  end
end

module Main
  using RefinementsInside
  Math.pi #=> refined method
end

Math.pi #=> original method

Explanation:

Defining a module #method is equivalent to defining an instance method on its #singleton_class.