Ruby on Rails FAQ

 1. Keyword delegate pada Model

Contoh kasus penggunaan keyword delegate

class University < ActiveRecord::Base

  has_many :lecturers

end

class Lecturer < ActiveRecord::Base

  belongs_to :university

end

[1] pry(main)> my_lecturer = Lecturer.find('459352183')

=> “Agung Supriadi”

[2] pry(main)> my_lecturer.university.abbreviated_name

=> “BINUS”

[9] pry(main)> my_lecturer.university.address

=> “Jl. Kebon Jeruk Raya No. 27, Kebon Jeruk”

Jika kita menggunakan keyword delegate, maka kita bisa mengakses lebih cepat:

class Lecturer < ApplicationRecord

  belongs_to :university

  delegate :abbreviated_name, :address, to: :university

end

[10] pry(main)> my_lecturer.abbreviated_name

=> “BINUS”

[11] pry(main)> my_lecturer.address

=> “Jl. Kebon Jeruk Raya No. 27, Kebon Jeruk”

Bagaimana jika my_lecturer pun punya address? maka kita bisa gunakan prefix pada delegate

class Lecturer < ApplicationRecord

  belongs_to :university

  delegate :abbreviated_name, :address, to: :university, prefix: true

  def address

    "this is address of the lecturer"

  end

end

[21] pry(main)> my_lecturer.address

=> "this is address of the lecturer"

[22] pry(main)> my_lecturer.university_address

=> “Jl. Kebon Jeruk Raya No. 27, Kebon Jeruk”

Atau menggunakan custom prefix

class Lecturer < ApplicationRecord

  belongs_to :university

  delegate :abbreviated_name, :address, to: :university, prefix: :campus

  def address

    "this is address of the lecturer"

  end

end

[22] pry(main)> my_lecturer.campus_address

=> “Jl. Kebon Jeruk Raya No. 27, Kebon Jeruk”