Question

What’s the best practice for hiding variables in a Ruby file, like the equivalent of a (function() {})() closure in JavaScript?

So if I have a file:

foo = 5
bar = foo * foo

I only want to expose bar, not foo, when someone requires it.

Answer 1

If you have a file containing those two lines and someone requires that file, neither of the two variables will be exposed. Local variables are still local to the file even if they appear at the global scope.

If you want to expose bar, you’ll need to turn it into a global variable $bar or, if you don’t intend for the variable to change, into a constant Bar. By not doing the same thing to foo it will automatically not be exposed.

You might also consider wrapping the whole thing up in a module or class.