问题
Assume x is a gem, that contains both Hello and Goodbye classes.
If I write a program that require 'x', but only uses the Hello class. Is the Goodbye class loaded as well?
回答1:
You include scripts or files, not gems.
With
require 'x'
you load the file x.rb. Which x.rb you load is defined by the search path, the search pathes can be modified by gem definitions (what you didn't use in your example code).
Everything inside the file x.rb is loaded. If x.rb contains other require commands, those files are also loaded.
来源：https://stackoverflow.com/questions/10001106/does-requiring-a-gem-load-everything-including-things-i-dont-use