The Book of Ruby

Name Conflicts

Module methods (those methods specifically preceded by the module name) can help protect your code from accidental name conflicts. However, no such protection is given by instance methods within modules. Let’s suppose you have two modules—one called Happy and the other called Sad. They each contain a module method called mood and an instance method called expression.

happy_sad.rb

module Happy
    def Happy.mood        # module method
        return "happy"
    end

    def expression        # instance method
        return "smiling"
    end
end
module Sad
    def Sad.mood          # module method
        return "sad"
    end

    def expression        # instance method
        return "frowning"
    end
end

Now a class, Person, includes both these modules:

class Person include Happy include Sad attr_accessor :mood def initialize ...