When do you need to prefix Ruby constants with "::"? (uninitialized constant error) - Stack Overflow

The module nesting is primarily set by using the module and class keywords to open a class/module.If its not found there it will keep going upwards in the module nesting until it reaches main and if the constant still isn't found by then you'll get a missing constant error.This error can be somewhat confusing since the message contains the module nesting where it started looking for the constant.By prefix a constant with :: you're explicitly telling Ruby to resolve the constant from the top level namespace:.