The Book of Ruby

Module Methods

In addition to instance methods, a module may also have module methods. Just as class methods are prefixed with the name of the class, module methods are prefixed with the name of the module:

def MyModule.lose
    return "Sorry, you didn't win"
end

You can call a module’s module methods just as you would call a class’s class methods, using dot notation, like this:

MyModule.lose   #=> "Sorry, you didn't win"

But how do you call an instance method? Neither of the following attempts succeeds:

puts( prize )           # Error: undefined local variable or method
puts( MyModule.prize )  # Error: undefined method 'prize'

In spite of their similarities, classes possess two major features that modules do not: instances and inheritance. Classes can have instances ...