RE: Overridden methods
From: Michael Kraus (mkraus_at_wildtechnology.net)
Date: 11/25/04
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Date: Thu, 25 Nov 2004 11:42:01 +1100 To: "Bob Showalter" <Bob_Showalter@taylorwhite.com>, <beginners@perl.org>
G'day...
Firstly ***thanks*** to everyone who has been helping me with this....
Really appreciated...
Now, for friendly arguments sake...
> > I'm wanting to write a method in an abstract class that must be
> > overriden by it's children. If it is called directly (i.e. without
> > being overriden) then it registers an error, but if its
> called via an
> > overriding method then do some common functionality.
>
> That's not an abstract class.
Huh? I thought that was the definition of an abstract class... :)
According to:
http://developer.apple.com/techpubs/macosx/Cocoa/ObjectiveC/7objc_glossa
ry/chapter_9_section_1.html
"A class that's defined solely so that other classes can inherit from
it. Programs don't use instances of an abstract class, only of its
subclasses."
... and to: http://www.gwydiondylan.org/drm/drm_126.htm
"A class that cannot have direct instances. The opposite of an abstract
class is a concrete class."
... and to:
http://mcs.open.ac.uk/computing/html/new_courses/m301/glossary.htm
"[M206] A class that is not intended to have instances. An abstract
class is used to define a minimum message protocol for all its
subclasses. If the abstract class can implement the method directly then
it does so and the code is inherited by the subclasses. If it cannot
implement a working method (because the subclasses must implement the
method differently) then it defines a dummy method that raises an
exception if it is invoked, thus forcing all subclasses to over-ride the
method. This is a class which is never used to create objects, rather it
is used to specify the minimum set of messages to which any subclass (of
the abstract class) can respond, that is to say an abstract class
describes the common characteristics of its subclasses."
... is there something I'm missing... :)
But the help you've provided is excellent - thanks I appreciate it...!
:)
Regards,
Michael S. E. Kraus
Software Developer
Wild Technology Pty Ltd
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