Using RecordRef to Work with Multiple Tables - microsoft-dynamics

Question

I have a group of tables that I need to the integer key from and I would like to be able to pass in any of them into a single and get the next value for the key.
I believe that RecordRef is the way to do this, but the code so far doesn't seem quite right.
I am trying to build a function that will take a table record and then return an integer value, that integer value will be the next record for the primary key. IE: if the last record's key is is 62825 the function will return 62826.
FunctionA
BEGIN
Id := GetNextId(SalesRecord); //Assignment not allowed
END;
FunctionB
BEGIN
Id := GetNextId(CreditMemoRecord); //Assignment not allowed
END;
GetNextId(pTableReference: RecordRef) rNextId : Integer
BEGIN
CASE pTableReference.NUMBER OF
DATABASE::SalesRecord: BEGIN
//Find last Record
pTableReference.FINDLAST;
lFieldRef := pTableReference.FIELD(1); //Set to the PK field
END;
DATABASE::CreditMemoRecord: BEGIN
//Find last Record
pTableReference.FINDLAST;
lFieldRef := pTableReference.FIELD(10); //Set to the PK field
END;
... //do more here
END; //CASE
EVALUATE(rNextId,FORMAT(lFieldRef.VALUE)); //Get the integer value from FieldRef
rNextId := rNextId + 1; //Add one for the next value
EXIT(rNextId); //return the value
END;
With this code I am getting the error "Assignment is not allowed for this variable." on the Function Call to GetNextId
Idea of the Table Structure:
Table - SalesRecord
FieldId, Fieldname, Type, Description
1 id integer PK
2 text1 text(30)
3 text2 text(30)
4 dec1 decimal
5 dec2 decmial
Table - CreditMemoRecord
FieldId, Fieldname, Type, Description
10 id integer PK
20 text1 text(30)
30 text2 text(30)
40 dec1 decmial
50 dec2 decmial

Answer 1

Just put function like this in both tables
GetNextId() rNextId : Integer
BEGIN
RESET;
FINDLAST;
EXIT(id+1);
END;
an then call it from record variable
FunctionA
BEGIN
Id := SalesRecord.GetNextId();
END;
FunctionB
BEGIN
Id := CreditMemoRecord.GetNextId();
END;
This is common practice I believe.

Answer 2

You mean "GetNextValue" get next record? I don't quite understand your use-case.
If you want to pass in a generic record, then you'll want to use the VARIANT data type. This is a wildcard type that will accept Records from any table, and allow you to return records from any table.
This is untested, but hopefully give you an idea of how they could work;
LOCAL NextRecord(VAR RecVariant : Variant)
IF RecVariant.ISRECORD THEN BEGIN
RecRef.GETTABLE(RecVariant);
// RecRef.NUMBER is useful for Database::"Customer" style comparisons
RecRef.NEXT;
RecRef.SETTABLE(RecVariant); // Might not be necessary
END;