Where to put/store/save/keep your modules and files containing modules?

To a Rails newbie, sometimes the simplest things are hard to figure out. Here's what you need to know:

When you create a module, you save it to your lib/ directory.

All the modules in the lib/ directory are auto-loaded by Rails. That is, Rails does something like this:

for file in lib/
   require file
end

Also, I think there is some magic to this, but I'm not 100% sure. If you have a module called MiscUtils then your file needs to be named misc_utils.rb in order for Rails to auto-load it.

Additionally, Ruby does this super-sweet thing where you can re-open any class or module and add to it at any time. In other words, you can declare a class or module in two locations, and Ruby will merge them together and treat them as one class. My experience has been that when you do this, then you need to explicitly require the files even if they're in the lib directory.