Add method to base class in the context of module

Question

I want to add a custom method to String class in Ruby. I am aware that it can be done with following code:

class String
  def my_own_method
    # impelementation comes here 
  end
end

If I write that code in a file say "string.rb" and somewhere else i.e. in irb, I write require "string" then it works quite fine and I have access to that custom method on any string object. However, the problem arises when I want to package my custom code into a module like this:

module A
  class String
    def my_own_method
      # implementation
    end
  end
end

Then when I include the module (with no error), I don't have access to the method on each string object unless I instantiate directly an string by calling, say,s = A::String.new. In that case I have access to my custom method but only for the s variable not on any string object. What shall I do to both package my util classes and automatically add their methods to base classes? Any help is really appreciated.

Answer 1

One option is to use :: to ensure you are grabbing the top-level String class:

module A
  class ::String
    def my_own_method
      self.reverse
    end
  end
end

"some string".my_own_method # => "gnirts emos"

I also have to agree with Sergio's point at the end of his answer. Not really sure of the need to do this.

Answer 2

Well, for one thing, you can use class_eval

module A
  String.class_eval do
    def my_own_method
      self.upcase
    end
  end
end


'foo'.my_own_method # => "FOO"

But if I were you, I'd go with opening a String class in the global scope (your first snippet). I don't really see the reasons not to do it.