CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3
deamon
deamon

Reputation: 92387

Why are callbacks callable in Rails model classes?

I have a Rails model class like this:

class Something < ActiveRecord::Base

  before_create do
     self.key = SecureRandom.urlsafe_base64(8)
  end

end

Why can I call before_create here? I expected it to be a method of ActiveRecord::Base but it is not. Callbacks are methods of ActiveRecord::Callbacks. But why can I call them in a model class without including something?

Upvotes: 2

Views: 325

Answers (3)

kreek
kreek

Reputation: 8834

Callbacks are a Module within ActiveRecord that Module is then 'mixed in' to Base which 'Something' extends. Modules/Mixins are kind of like interfaces in some static languages but they also include the implementation of a method rather than just a contract to implement it.

Upvotes: 1

lucapette
lucapette

Reputation: 20724

Because ActiveRecord::Base includes it for you. See https://github.com/rails/rails/blob/master/activerecord/lib/active_record/base.rb#L2135

Upvotes: 2

mu is too short
mu is too short

Reputation: 434615

You can do that because ActiveRecord::Base does this (or something similar depending on your version of Rails):

Base.class_eval do
  #...
  include Callbacks, ActiveModel::Observing, Timestamp
  #...
end

So ActiveRecord::Base already includes ActiveRecord::Callbacks and your class picks up the callbacks by inheriting from ActiveRecord::Base.

Upvotes: 3

Related Questions