define_callbacks(*callbacks) public

Define sets of events in the object lifecycle that support callbacks.

define_callbacks :validate
define_callbacks :initialize, :save, :destroy
  • :terminator - Determines when a before filter will halt the callback chain, preventing following callbacks from being called and the event from being triggered. This is a string to be eval’ed. The result of the callback is available in the result variable.

    define_callbacks :validate, :terminator => "result == false"

    In this example, if any before validate callbacks returns false, other callbacks are not executed. Defaults to “false”, meaning no value halts the chain.

  • :rescuable - By default, after filters are not executed if the given block or a before filter raises an error. By setting this option to true exception raised by given block is stored and after executing all the after callbacks the stored exception is raised.

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

    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.

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