Delegates in Rails with simple example

03 December 2018 - less than 1 min read time
Tags: Ruby LastMinutePrep

In Rails, delegates allow you to forward method calls from one object to another. This is useful when you want to delegate the responsibility of handling certain methods to another object. Let’s illustrate this with a simple example:

Suppose you have a User model and an Address model, and each user has an associated address. You want to be able to access address attributes directly from the user object without having to explicitly call the address object each time. This is where delegates come in handy.

Here’s how you can use delegates:

class User < ApplicationRecord
  has_one :address

  # Delegate methods from the address object to the user object
  delegate :city, :state, :zipcode, to: :address
end

class Address < ApplicationRecord
  belongs_to :user
end

In this example, we have a User model with a has_one :address association, indicating that each user has one associated address. We then use the delegate method to delegate the city, state, and zipcode methods from the address object to the user object.

Now, you can access address attributes directly from a user object:

user = User.first
puts user.city
puts user.state
puts user.zipcode

Behind the scenes, Rails will forward these method calls to the associated address object, making it appear as if the user object itself has these methods. This helps keep your code clean and concise by avoiding unnecessary method chaining and delegation logic.