Accessing module methods with ::

Question

Documentation I\'ve read tells me to use Module.method to access methods in a module. However, I can use Module::method as well. Is this syntactic sugar, or am I confused?

Answer 1

The :: is called scope resolution operator, which is used to find out under what scope the method, class or constant is defined.

In the following example, we use :: to access class Base which is defined under module ActiveRecord

ActiveRecord::Base.connection_config
# => {:pool=>5, :timeout=>5000, :database=>"db/development.sqlite3", :adapter=>"sqlite3"}

We use :: to access constants defined in module

> Cat::FURRY_LEVEL
=> 4
> Cat.FURRY_LEVEL
=> undefined method `FURRY_LEVEL' for Cat:Module (NoMethodError)

The . operator is used to call a module method(defined with self.) of a module.

Summary: Even though both :: and . does the same job here, it is used for different purpose. You can read more from here.