Ruby does not support Multiple Inheritance. Ruby uses Mixin instead.

Ruby does not support Multiple Inheritance, but Ruby supports Multilevel inheritance. Some languages like C++, Perl and Python support Multiple inheritance and some like Java, C# don’t. Ruby uses Mixins to get this problem solved. Didn’t get a clear picture…? Let’s get it then 🙂

Inheritance is one of the most important OOPS concept. When a class B inherits from class A, class A becomes superclass and class B is child class of class A. All the properties of class A is applicable to class B.

What is Multilevel inheritance…?

When there is more than one level of inheritance, it’s MultiLevel Inheritance. Say, when class B inherits from class A, and class C inherits from class B, class C gets all properties from class B, class B gets all properties from class A. Simply stating,

class B inherits class A
class C inherits class B

it is Multilevel inheritance. This is supported by Ruby.

class Animal

  def my_method
    puts "Hi, I am a #{self.class}"
  end

end


Class Bird < Animal

  def method_2
    puts "#{self.name} can fly high"
  end

end

Class Eagle < Bird

  def method_3
    puts "Hi, I can fly above clouds!"
  end

end

Animal.new.my_method # => "Hi, I am a Animal"
Bird.new.my_method # => "Hi, I am a Bird"
Bird.new.method_2 # => "Bird can fly high"
Eagle.new.method_2 # => "Eagle can fly high"
Eagle.new.method_3 # => "Hi, I can fly above clouds!"

What is Multiple inheritance...?

When a class is inherited from multiple class at the same time, we call it Multiple inheritance. Say, class C is inherited by class A as well as class B.

class C inherits class A
class C inherits class B

The above is not possible in ruby, but ruby makes use of Mixin to solve the above. We include a module inside a class, which gives same functionality as of Multiple inheritance.

module Animal

  def my_method
    puts "Hi, I am a #{self.class}"
  end

end

module Mammal

  def method_2
    puts "#{self.name} is a Mammal"
  end

end


class Dog
  include Animal
  include Mammal

  def method_3
    puts "hey, I am faithful"
  end

end

Dog.new.method_3 # => "hey, I am faithful"
Dog.new.method_2 # => "Dog is a Mammal"
Dog.new.my_method # => "Hi, I am a Animal"