Nested modules are not what they seem. In this post, Rishi talks about the scope among nested variables. Here’s an Ah-ha! moment for you!
When we define nested modules like this:
and when we do like this:
Even though both method calls to print_const looks same, and should return same result. But it returns different values of the constant.
Reason:
When you do this in first case:
and this gives:
So ruby looks for the constant X in the order as A::B::C, A::B, A. and it loads wherever it finds first, and as in our scenario, under module B.
And in second scenario:
and this gives:
Here since the nesting of the module is different, it only search in A::B::C and A, skipping A::B. So it finds constant X under module A.
Josh Software 