define_callbacks

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

Options

• :terminator - Determines when a before filter will halt the callback chain, preventing following callbacks from being called and the event from being triggered. This should be a lambda to be executed. The current object and the return result of the callback will be called with the lambda.

  1	define_callbacks :validate, terminator: ->(target, result) { 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.

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

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

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  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

  1	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 âkindâ is âbeforeâ and ânameâ is âsaveâ. 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

  1	define_callbacks :save, scope: [:name]

  would call Audit#save.