Re: Procedure pointers - can I do this??

[Scott Klement <rpg400-l@xxxxxxxxxxxxxxxx>]

[SNIP]
> 1. What is SCOPE  of myEventHandler and myErrorHandler??? I mean, can I
> manipulate with Var1, Var2 ... VarN from MODUL A if subp implementation is
> in ModulB

They're normal subprocedures that follow the same rules as any other 
subprocedure. Aside from their own local variables, they can only use 
global variables in the same module, unless they're passed as parameters 
or IMPORTed from the activation group. Same as any other procedure.

> 2. If I can't acess VAR1, VAR2... VarN has anyone any IDEA how to make
> them accessible??? EXPORT them (how can I do that???) or to define
> USERSPACE that will hold neaded data and would be visible in MODULE B and
> MODUL A???

Personally, I like to pass them as parameters.  In an object-oriented 
language, you'd typically have a bunch of variables that are part of the 
class. To do the same thing in RPG, define a data structure for all of 
these "class" variables, and pass it as a parameter to every procedure in 
that "virtual class".  Qualified data structures work really nicely for 
this, because you can define them as templates in a /copy member, and use 
LIKEDS to define them the same way everywhere (if that makes any sense.)

When working with call-backs, I also like to have an ordinary space 
pointer that the calling procedure can pass to the service program, and 
expect the service program to pass back to every call-back.  That's really 
useful because you can attach any data that you like, and have it 
available in every callback procedure.  Makes the service programs more 
versatile.

> 3. If I want to write to PF named logPF in myEventHandler where should I
> define that file in MODUL A or MODUL B??? (My Idea is that file is defined
> in MODUL B so the interface could be more flexible)

Again, it's an ordinary subprocedure.  The files must be defined in the 
same module, as is always the case with any subprocedure in any RPG 
program.

You could, of course, use the ILE C runtime library's _Ropen(), _Rreadn(), 
etc functions if you needed a file that's shared across module boundaries.

> 4. Is there any literature/link/book/pdf which describes procedure
> pointers more detailed than Sourcers guide???

There have been some magazine articles written, though I haven't read them 
so I can't really make recommendations.

> From my perspective, once you know you can get the address of a procedure, 
and you can call a procedure at a given address, there's very little else 
to say.  The rest is the same as any other subprocedure call anywhere.