Modules & Mixins

💎 Ruby Lesson 13 Advanced

Ruby classes can only inherit from a single parent class. To achieve multiple inheritance, Ruby provides Modules and Mixins.

1 Mixins vs Namespaces (include vs extend)

Modules wrap reusable methods and constants. Unlike classes, modules cannot be instantiated. They have two primary use cases:

Namespaces: Groups related classes to prevent naming collisions.
Mixins: Injects module methods directly into a class using the **`include`** keyword (methods act as instance methods) or **`extend`** keyword (methods act as class methods), implementing clean multiple inheritance.

2 Mixins Code

Let's run a program defining modules and mixing their methods into classes:

Ruby — Modules and Mixins ▶ Run Code

module Flyable
  def fly
    "I am flying high!"
  end
end

module Swimmable
  def swim
    "I am swimming fast!"
  end
end

class Duck
  # Mixin both modules to achieve multiple inheritance
  include Flyable
  include Swimmable
end

donald = Duck.new
puts donald.fly
puts donald.swim

3 Code Challenge

Challenge: Create a module called `Loggable` with a method `log(message)` that prints a timestamped message. Include the module in a class called `Database` and invoke the `log` method.