Re: Can RPGLE simulate OO programming?

["David Morris" <dmorris@xxxxxxxxxxxxx>]

Barbara,

I would say one of the fundamental problems in the lack of built in support for 
parameterized types.  If this were supported, we could write code that 
stimulated 
sub-classing and overloading.

David Morris

>>> bmorris@ca.ibm.com 02/18/00 04:23PM >>>

...Two problems were identified that RPG "couldn't solve": multiple
instances and calling different methods.  Allocating memory for a
data structure solves the problem of having multiple instances of
the object.

To handle different classes of objects calling different methods,
have only one external method, but have it check if the object
requires a different method and call that method if necessary.
If you didn't want a class to know about its subclasses, you
just need to have a way for subclasses to register alternate
methods with the class.  When you create a new subclass object,
you call a procedure in the class that tells the class that for
method X, it should call method SUB_X instead for this particular
object.  Then when it gets called, it looks up the object and
calls through to the overriding method.

Barbara Morris


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