I often see custom Exception classes inheriting from StandardError.
Errors which you can generally deal with are subclassed from
StandardError:
module AbstractController
class Error < StandardError #:nodoc:
end
class ActionNotFound < StandardError #:nodoc:
end
unless action_name = method_for_action(action_name)
raise ActionNotFound, “The action ‘#{action}’ could not be found for
#{self.class.name}”
end
But why even bother to create the subclasses (which as shown above,
have no definition of themselves), when substituting ActionNotFound
with StandardError during the raise call will have the same effect.
I would understand if there was some level of customization involved
that distinguishes it from the super class:
class DoubleRenderError < Error
DEFAULT_MESSAGE = “Render and/or redirect were called multiple
times in this action. Please note that you may only call render OR
redirect, and at most once per action. Also note that neither redirect
nor render terminate execution of the action, so if you want to exit
an action after redirecting, you need to do something like
“redirect_to(…) and return”.”
def initialize(message = nil)
super(message || DEFAULT_MESSAGE)
end
end
But in the exampels I provided in the initial post that was not the
case. ActionNotFound, for example, had no implementation of its own.
It seems to be a waste of memory allocation.
On Sunday, September 16, 2012 7:57:44 PM UTC+1, John M. wrote:
have no definition of themselves), when substituting ActionNotFound
with StandardError during the raise call will have the same effect.
Because it doesn’t have the same effect. Raising specific subclasses
allows
you to write targeted rescue clauses rather than rescuing
indiscriminately.