Define a method that is a closure in Ruby

Question

I\'m re-defining a method in an object in ruby and I need the new method to be a closure. For example:

def mess_it_up(o)
  x = \"blah blah\"

  def o.to_s
    pu         


        

Answer 1

Feature #1082 implemented in Ruby 1.9.2 makes this an easy task with Object#define_singleton_method:

def mess_it_up(o)
  x = "blah blah"

  # Use Object#define_singleton_method to redefine `to_s'
  o.define_singleton_method(:to_s) { x }
end

The concepts involved are still the same as in my previous answer, which provides a more in-depth description of how this works in Ruby's object model, as well as a Object#define_method definition that is conceptually the same as Ruby 1.9.2's Object#define_singleton_method.

Other methods that you might find useful for similar tasks:

• Object#singleton_class
• Object#singleton_methods
• Object#respond_to_missing? (great blog post here)