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method

define_callbacks

Importance_3
Ruby on Rails latest stable (v6.1.7.7) - 0 notes - Class: ActiveSupport::Callbacks::ClassMethods
define_callbacks(*names) public

Define sets of events in the object life cycle that support callbacks.

define_callbacks :validate
define_callbacks :initialize, :save, :destroy
Options
  • :terminator - Determines when a before filter will halt the callback chain, preventing following before and around callbacks from being called and the event from being triggered. This should be a lambda to be executed. The current object and the result lambda of the callback will be provided to the terminator lambda.

    define_callbacks :validate, terminator: ->(target, result_lambda) { result_lambda.call == false }
    

    In this example, if any before validate callbacks returns false, any successive before and around callback is not executed.

    The default terminator halts the chain when a callback throws :abort.

  • :skip_after_callbacks_if_terminated - Determines if after callbacks should be terminated by the :terminator option. By default after callbacks are executed no matter if callback chain was terminated or not. This option makes sense only when :terminator option is specified.

  • :scope - Indicates which methods should be executed when an object is used as a callback.

    class Audit
      def before(caller)
        puts 'Audit: before is called'
      end
    
      def before_save(caller)
        puts 'Audit: before_save is called'
      end
    end
    
    class Account
      include ActiveSupport::Callbacks
    
      define_callbacks :save
      set_callback :save, :before, Audit.new
    
      def save
        run_callbacks :save do
          puts 'save in main'
        end
      end
    end
    

    In the above case whenever you save an account the method Audit#before will be called. On the other hand

    define_callbacks :save, scope: [:kind, :name]
    

    would trigger Audit#before_save instead. That’s constructed by calling #{kind}_#{name} on the given instance. In this case “kind” is “before” and “name” is “save”. In this context :kind and :name have special meanings: :kind refers to the kind of callback (before/after/around) and :name refers to the method on which callbacks are being defined.

    A declaration like

    define_callbacks :save, scope: [:name]
    

    would call Audit#save.

NOTE: method_name passed to `define_model_callbacks` must not end with `!`, `?` or `=`.

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