How can you do a safe, backwards-compatible “reverse-monkeypatch” in Ruby?

Question

If your coworker "opens" ("monkeypatches") a class in Ruby and redefines some important functionality that you need to use, how do you access that original pre-monkeypatched functionality without breaking a system that already relies/has dependencies on his monkeypatched definitions?

Answer 1

Given the example of the method overriding, if you can get some code loaded before his monkey patch is loaded then you can alias the method.

class Fixnum
  alias_method :original_plus, :+
end

class Fixnum
  def +(x)
    self - x
  end
end

>> 5 + 3
=> 2
>> 5.original_plus(3)
=> 8

Answer 2

I recently saw this in the rubyflow feed - its a simple library that lets you namespace top level constants called aikidoka. Without any details of how/what is being monkey patched it is a bit tough to help. In theory though you could use an approach like this to namespace the monkey-patched version of the class so that you can access both it and the original independently.

Answer 3

Depends exactly what functionality was changed and in what way, but something implementing like Jim Wienrich's BlankSlate class may help: