RE: link list returned from service program

In the current version that I've, the caller will do below to walk the
link list that returned from the service program:
D myFamily ds
likeds(cumGetCustomerFamilyTree_Cust)
D based(myFamily_p)
D myFamilyHead ds
likeds(cumGetCustomerFamilyTree_Cust)
D based(myFamilyHead_p)

// call the export procedure to build/get the link list
myFamilyHead_p = cumGetCustomerFamilyTree(myCuNo);

// loop thru the link list
myFamily_p = myFamilyHead_p;
dow myFamily_p <> *null;
doSomthingWithThisFamilyMember(myFamily.number :myFamily.level);
myFamily_p = myFamily.next;
enddo;

// call the export procedure to destroy the link list
cumDestroyCustomerFamilyTree(myFamilyHead_p);



In the encapsulated version, I envision caller needs to do this:
// create a list
myFamilyID = cumBuildCustomerFamilyTree(myCuNo);

//loop thru the list
myRetCode = cumSetCustomerFamilyTree(myFamilyID: 'FIRST');
dow myRetCode > 0;
doSomthingWithThisFamilyMember(
cumGetCurrentFamilyMember_Number(myFamilyID)
:cumGetCurrentFamilyMember_Level(myFamilyID));
cumSetCustomerFamilyTree('Next');
enddo;

// call the export procedure to destroy the link list
cumDestroyCustomerFamilyTree(myFamilyID);


You are right that the encapsulated version is better, but the
complexity of creating this service program is conflicting with my
project due date :). Tough choice.



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Alan Campin
Sent: Wednesday, March 12, 2008 12:29 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: link list returned from service program

<snip>

Encapsulation is a good thing.

Indeed. As a general rule, return a pointer to the program to the

structure which is managed by the service program itself (i.e. allocated
and destroyed).
The program only knows about the pointer, it knows nothing about the
internal structure. Then pass this pointer as the first argument to
procedures "GetNextCustomer", "GetParentCustomer". And if you put all
the code like this that belongs to the Customer entity into one
well-named serviceprogram then we even have a bit of OO here.
</snip>

<clip>

The downside to service programs, if you would call it that, is that
they take a lot of work to create. It is more difficult to create a
general purpose service program than a single purpose program but the
results are almost always worth it.

</clip>