I’ve noticed one of the problems I have writing this blog is that I prefer to have finished thoughts when I write up something, or at least to have a good understanding of a problem I am working on before committing it to ‘paper’. Unfortunately, this doesn’t lead to many updates. I’ll try to break this habit a little. Recently I heard the term ‘Monkey Patching’ after one of the Seattle Patterns Group meetings, in relation to Ruby on Rails.
A Monkey-Patch (also called Monkey Patch, MonkeyPatch) is a way to extend or modify runtime code without altering the original source code for dynamic languages (e.g. Ruby and Python).
Today, reading a blog entry from Chad Fowler, the term came up again with a Python developer saying:
You can monkeypatch code in Python pretty easily, but we look down on it enough that we call it “monkeypatching”. In Ruby they call it “opening a class” and think it’s a cool feature. I will assert: we are right, they are wrong.
When I read that, I felt almost relieved, because I was thinking the same thing. I can see a limited use for it, but it seems like something you should only do in dire circumstances, that it would be detrimental to good software engineering practices. I can’t prove this, nor am I totally convinced, but Ruby and Ruby on Rails in particular seems to play a little bit fast and loose. I suppose this fits in with Agility, but there does seem to be a mental divide between Python and Ruby people (even though they are really quite close linguistically). To date, I’m much more in the Python camp, but I’ve been deploying Rails apps at work, and I’ll be delving more into Ruby as I go forward. I have heard rumors that Zope does Monkey Patching, and this convinces me even more. Zope has almost single handedly destroyed Python’s reputation at my place of work. Thanks Zope!