| Re: Abstract Objects and Methods [message #12111] |
Tue, 23 June 1998 00:00  |
Phillip & Suzanne
Messages: 31
Registered: June 1998
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Member |
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J.D. Smith wrote:
>
> Phillip David wrote:
>>
>> Does anyone know of any way to make sure a method has been overriden by a
>> child class? The only thought I have is to make the class return a
>> {structure/object/status} that contains a status code, with one specifying
>> that the abstract routine was invoked rather than the concrete subclass of the
>> abstract routine. Any better ideas?
>>
>> Phillip
>
> How about just:
>
> pro Abstract::aMethod, arg1, arg2
> message, 'This is an abstract method and must be overridden in class
> '+obj_class(self)
> end
>
> with the understanding that aMethod not be chained to in the overridding
> method of a subclass? Or am I missing something?
J.D. -- This is perfect. Thanks for the tip. BTW, this also works for making
the Init function abstract.
--- sample ---
pro abstract::method
message, 'Method is abstract in class abstract'
end
function abstract::init
message, 'Class abstract is abstract and cannot be instantiated'
end
pro abstract__define
struct = {ABSTRACT, NULL:0b}
end
--- end of sample ---
By the way, I also learned another important lesson about objects. Be sure
you define both an init function (even if it only returns the value '1' (i.e.,
success)) and a cleanup routine (even with an empty body). When running IDL
5.1 under Win/NT, a class with an implicit Init and Cleanup takes about 4
seconds for each operation. When the operations are defined explicitly, even
with empty bodies, the operations are almost instantaneous.
Phillip
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