RE: OO in RPG

[Scott Klement <klemscot@xxxxxxxxxxxx>]

The address of the procedure doesn't need to be known at compile time, 
it needs to be known at bind time. :)

The difference is subtle, but its useful.  In particular, I have service 
programs that get data and need to write it somewhere, but depending on
the application, where they write it can be different.  So I pass them
procedure pointers, and they call the given procedure to write the data.

If I want to write it to a stream file, for example, I can pass the
address of the IFS "write" procedure.  Similarly, I can provide my own
procedure, in the same format as "write", if I want to do something else
with it. 

I don't need these to be "truly dynamic", and I appreciate the speed
improvement that binding them gives me -- but at the same time, I don't
want to recompile the service program for every new application that uses
the routines -- and this is why its important that the addresses are
resolved at bind time.

Make sense?


On Tue, 5 Dec 2000, Peter Connell wrote:

> Jon has already alluded to the fact that the standard use procedure pointers
> only gives the illusion of dynamic procedure calls. In other words the
> procedure call is dynamic only in the sense that it points to a procedure
> whose address was resolved at compile time or when the program was activated
> in the case of a service pgm, unlike the old dynamic calls that are resolved
> only at runtime. It means that you can benefit by coding a call using a
> procedure pointer but you still have to include code that initializes all
> the pointers by assigning them the address of the corresponding procedure.
> So you are in effect still hard coding all the procedure calls.
> 
> To obtain a truly dynamic procedure call that is not known at compile time
> you must you the special API's that permit you to force the activation of a
> service pgm and provide access to the procedures within.
> 
> Cheers, Peter
> 

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