Ruby association example

ruby-assoc-belongs-to.rb

require 'faker'

module BelongsToAssociation
  def self.included(receiver)
    receiver.extend ClassMethods
  end

  module ClassMethods
    def belongs_to(attribute)
      class_eval do

        define_method("#{attribute}=") do |value|
          instance_variable_set("@#{attribute}", value)
            association_name = self.class.to_s.downcase + 's'
            send(attribute).send(association_name).push(self)
        end
      end
    end
  end
end

class User
  attr_reader :posts

  # has_many :posts
  
  def initialize
    @posts = []
  end
end

class Post
  attr_reader :user

  include BelongsToAssociation

  belongs_to :user
  # belongs_to :comment
  # belongs_to :image
  
  def initialize(user:)
    @title    = Faker::Name.title
    self.user = user
  end

  def to_s
    "Post##{self.object_id}: #{@title}"
  end
end

user = User.new

5.times { Post.new(user: user) }

user.posts.pop
puts user.posts

ruby-assoc.rb

require 'faker'

class User
  attr_reader :posts
  
  def initialize
    @posts = []
  end
end

class Post
  attr_reader :user
  
  def initialize(user:)
    @title    = Faker::Name.title
    self.user = user
  end

  def user=(user)
    @user = user
    user.posts.push(self)
  end

  def to_s
    "Post##{self.object_id}: #{@title}"
  end
end

user = User.new

5.times { Post.new(user: user) }

user.posts.pop
puts user.posts