Here's the scoop. Mixins (using Modules as a way to provide multiple inheritance) allow you to provide instance variables. If I create an @myString instance variable in my mixin, and then in my class which includes it I also have an instance variable with the same name it can all go horribly wrong.
But here's the pain. In nice statically checked land, the compiler (best chum o' mine) will flag my goof. In Ruby-land, there is no compiler. Things might even work for a while. Worse still they miht break without my knowing it. Then finding the problem would be pretty nasty and debug-steppy.
Now I know I should have created a nice set of unit tests to avoid this, but in a complex application I can see things like this falling between the cracks; horrible nasty cracks with spikes and stuff at the bottom. Yurgh!
Or am I just being over sensitive?
Before I close, there are a few other confusions this deceptively short chapter threw up:
- I thought everything in Ruby was a class. Even objects. How come then Pickaxe states "a module isn't a class" (page 119). Hmmm.
- include / require / load / aaaaarhg! I like Java's "import" better and despite the problems, classpaths sheild the rest from me in 90% of situations (though heaven forbid when I have to debug a classloader problem, or worst still, implement one of my own...)