ActiveRecord hooks add addition capability that developers may find very useful. These hooks run some code when you try to add, delete or update a database.

ActiveRecord has two different ways when it comes to hooks implementation: ActiveRecord::Observer and callbacks

ActiveRecord callbacks implemented as part of ActiveRecord::Base class and include: before_save, after_save among others. Here is an example of running after_create callback in ActiveRecord implementation.

class MyClass < ActiveRecord::Base
 def after_create
  puts %{Record was created}
 end
end

my_class = MyClass.create(:name => ‘Title’) //This line will save an object of MyClass type and will call of after_create method.

ActiveRecord callbacks are good for single action and it is not very suitable for multiple actions. In order to accommodate multiple actions after certain event, you can start using ActiveRecord::Observer. It is available from the rails-observer gem. Observers can watch a single class in your code.

In order to implement Observer, you need to create new method of the class that inherit Observer Class as shown in the example below

class MyClass < ActiveRecord::Base
end

class MyClassObserver < ActiveRecord::Observer
 observe MyClass
 
 def after_create
   puts %{Record was created}
  end
end

my_class = MyClass.create(:name => ‘Title’) //This line will save an object of MyClass type and will call of after_create method

Please note that in order for Observer to fire an event, you need to add the following snippet of the code into application.rb file

config.active_record.observers = :class_observer

Please note: if you name your Observer class after method you try to observer, then you don’t need to include class you want to observer inside the method. We presented both ways in one example above.