Calling a method of a Ruby Singleton without the reference of 'instance'

Question

I would like to call a method of a Singleton Object without the reference to its instance

SingletonKlass.my_method

instead of

S         


        

Answer 1

Here is an alternative that does not really fall under the scope of my first answer. You can create a mixin module that undefines all the methods of the base class and then uses the method_missing technique:

module SingletonRedirect
  def included(base_class)
    instance = base_class.instance
    base_class.class_eval do
      methods.each &undef_method

      define_method :method_missing do |name, *arguments|
        instance.public_send name, *arguments
      end
    end
  end
end

To implement the idea, instance is a local variable that is passed via closure to the blocks in the calls to Class#class_eval and Module#define_method. Then, we do not need to refer to it by base_class.instance, so we can clear out all the methods, including that one (a technique known as a blank slate). Then, we define a method redirection system that takes advantage of the flat scope to refer to instance as a variable and call only methods that are publicly available via Object#public_send.