Understanding Ruby Modules: Prepend vs. Include

Introduction:

• Module is a collection of constants, methods, classes, and variables in a container.

• Modules implement the mixin facility

    module Animal
      def sound
        puts 'animal sound'
      end
    end
  

•     class Dog
        include Animal 
      end
  

  now we can access bark method

•     Dog.new.sound # animal sound
  

  you can overwrite the sound method in Dog class

    class Dog
      include Animal 
  
     def sound
        puts 'bark'
      end
    end
  
    Dog.new.sound # bark
  

  what if we replace include to prepend

    class Dog
      prepend Animal 
  
     def sound
        puts 'bark'
      end
    end
  
    Dog.new.sound #animal sound, why I defined a sound method in a subclass?
  

  although we have overwritten the sound method in Dog class we called it returned the module method because we need to understand the ancestries chains

• what are the ancestries chains?
  - the path of inheritance leading up to a given class or module

    class Dog
      include Animal 
  
     def sound
        puts 'bark'
      end
    end
  
    Dog.ancestors # [Dog Animal Object Kernel BasicObject]
  

    class Dog
      prepend Animal 
  
     def sound
        puts 'bark'
      end
    end
  
    Dog.ancestors # [Animal Dog Object Kernel BasicObject]
  

  using prepend makes Animal Method be executed over The dog method itself and no longer able to overwrite it

Conclusion:

• Ruby modules are a powerful feature for organizing and reusing code in Ruby programs.

• Understanding how to define, include, and extend modules is essential for effective Ruby programming and code design.

Additional Resources:

• https://blog.daveallie.com/include-vs-prepend

• https://www.mintbit.com/blog/understanding-ancestor-chains-in-ruby
  https://evanahouse.medium.com/inheritance-in-ruby-the-ancestors-chain-65c813aea71