Active Model Callbacks

Provides an interface for any class to have Active Record like callbacks.

Like the Active Record methods, the callback chain is aborted as soon as one of the methods throws :abort.

First, extend +ActiveModel::Callbacks+ from the class you are creating:

class MyModel
  extend ActiveModel::Callbacks
end

Then define a list of methods that you want callbacks attached to:

define_model_callbacks :create, :update

This will provide all three standard callbacks (before, around and after) for both the :create and :update methods. To implement, you need to wrap the methods you want callbacks on in a block so that the callbacks get a chance to fire:

def create
  run_callbacks :create do
    # Your create action methods here
  end
end

Then in your class, you can use the before_create, after_create, and around_create methods, just as you would in an Active Record model.

before_create :action_before_create

def action_before_create
  # Your code here
end

When defining an around callback remember to yield to the block, otherwise it won’t be executed:

around_create :log_status

def log_status
  puts 'going to call the block...'
  yield
  puts 'block successfully called.'
end

You can choose to have only specific callbacks by passing a hash to the define_model_callbacks method.

define_model_callbacks :create, only: [:after, :before]

Would only create the after_create and before_create callback methods in your class.

NOTE: Calling the same callback multiple times will overwrite previous callback definitions.

activemodel/lib/active_model/callbacks.rb