Ruby inheritance and delegation

I don't know much about the proper use of inheritance and delegation, so I summarized it.

Inheritance

It is to take over the function from another class and create a new class.

Example

Create a Foo class by inheriting all the methods from the Base class

class Base
  def message
    'ok'
  end
end

class Foo < Base; end
  
foo = Foo.new
puts foo.message
# => ok

transfer

It is to delegate a specific process (responsibility) to a method of another class.

Example

Delegate the message method of the Base class to the Foo class

class Base
  def message
    'ok'
  end
end

require 'forwardable'
class Foo
  extend Forwardable
  attr_reader :mess

  def initialize
    @mess = Base.new
  end
  def_delegator :mess, :message
end
  
foo = Foo.new
puts foo.message
# => ok

Scenes that use inheritance

Same role

Whether you are a fledgling engineer or an experienced Tsuyotsuyo engineer, the role of a programmer is the same. So, let's inherit the Progurammer class and inherit the function as it is.

class Programmer
  def initialize(type, langages)
    @type = type
    @langages = Array(langages)
  end

  def type_is
    puts "I#{type}is."
  end

  def langage_is
    str = ''
    langages.each do |lang|
      str += "#{lang} "
    end
    puts "I#{str}Can handle the language of"
  end

  def klass_is
    str = case self.class.name
    when 'TsuyoTsuyo'
      'Strong engineer'
    when 'Kakedashi'
      'Fledgling engineer'
    end

    puts "I#{str}is."
  end

  private
  attr_accessor :type, :langages
end

class TsuyoTsuyo < Programmer; end

class Kakedashi < Programmer; end

tsuyo = TsuyoTsuyo.new('Backend', %w[C C++ Python Go Ruby])
tsuyo.type_is
tsuyo.langage_is
tsuyo.klass_is

kake = Kakedashi.new('Frontend', %w[HTML CSS jQuery])
kake.type_is
kake.langage_is
kake.klass_is

Scenes using delegation

I want to use some functions although the roles are different

Programmers and designers have different roles. So in this case we will use delegation and only the type_is method will be inherited from the Programmer class.

require 'forwardable'
class Programmer
  def initialize(type, langages)
    @type = type
    @langages = Array(langages)
  end

  def type_is
    puts "I#{type}is."
  end

  private
  attr_accessor :type, :langages
end

class Designer
  extend Forwardable

  def initialize(type, skills)
    @programmer = Programmer.new(type, nil)
    @type = type
    @skills = Array(skills)
  end

  def_delegator :@programmer, :type_is

  private
  attr_accessor :type, :skills
end

class IkeIke < Designer; end

ikeike = IkeIke.new('WebDesigner', %w[HTML CSS Adobe JavaScript])
ikeike.type_is #This type_is method`Programmer`Method inherited from class

Summary

Thank you for reading this far. I hope it will be an opportunity to review my code.

I usually develop web services with Rails, but I don't think there are many occasions to use delegation. It is also true that I used to say "inheritance !!" It is difficult to judge whether the inheritance relationship is good or whether it is better to use delegation, but in the future I decided to implement it including the option of using delegation.