Rails Delegate Set Value

Question

I have a User.rb model and a UserSetting.rb model that i would like to delegate to (both getter and setter methods).

in user.rb

delegate :email_opt_in, :email_opt_in=, :to => :user_setting

At first glance this works great.

user = User.find(1)
user.email_opt_in #=> false
user.email_opt_in = true
user.save
user.email_opt_in #=> true

But looking closer the, user.save doesn't propagate to the UserSetting model.

User.find(1).email_opt_in #=> false

(So the value didn't get saved to the database).

This is my question: How can I get UserSetting to save automatically when one of its attributes are changed and then saved by its user?

This should only happen when a UserSetting attribute is changed otherwise every time a user is saved to the database it will trigger an additional un-needed & unwanted write to the database.

Answer 1

In your User model for user_setting association use autosave: true

class User < ActiveRecord::Base
  has_one :user_setting, autosave: true

  delegate :email_opt_in, :email_opt_in=, :to => :user_setting
end

Answer 2

I would explore using an ActiveRecord callback for this. I'm not sure which would make the most sense in your case, but before_update or after_update seem logical. In your callback, you would need to manually trigger a save call on the UserSetting object associated with the User. There's probably dozens of ways to accomplish this, but something along these lines should work:

class User < ActiveRecord::Base
  after_update do |user|
    user.user_setting.save if user.user_setting.changed?
  end
end