This may be what you're looking form, to add a method to a single instance, although the syntax is clearly not as smooth: https://stackoverflow.com/questions/18

This may be what you're looking form, to add a method to a single instance, although the syntax is clearly not as smooth: https://stackoverflow.com/questions/1887845/add-method-to-an-instanced-object https://stackoverflow.com/questions/1887845/add-method-to-an... OTOH, if your problem is slightly different, I find the syntax to add methods to any class very practical and powerful, with of course the caveat that you can produce a maintainability nightmare if overused: irb(main):001:0> a = 1 => 1 irb(main):002:0> class Integer irb(main):003:1> def hello irb(main):004:2> puts "world" irb(main):005:2> end irb(main):006:1> end => :hello irb(main):007:0> a.hello world => nil