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.    •
: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 callbac