Re: RPG UDDS Generic File Display/Update (Null fields in program described files)

[Frank Kolmann <frank.kolmann@xxxxxxxxx>]

Thanks Buck

After some attempts to cater for NULL values I have figured out that 
UDDS is fundamentally in conflict with NULL values.
UDDS requires a program described Display file, and ANY program 
described file makes the RPG compiler create the program with ALWNULL(*NO).
Further, Full Free Form RPG does not allow Program described files so 
UDDS has effectively gone the way of the Dodo.

The only possible way out of the dilemma is to have a separate program 
that does the file updates calling the C  Ropen/Rwrite etc functions.
I think I will try the split out into a separate program.
However the question remains how  the UDDS display program sets fields 
to null, I think field/exit will clear a field to null, but most 
probably it will be too messy if not impossible.
Possibly separate modules some with ALWNULL(*USRCTL) some with 
ALWNULL(*NO) but I suspect this will cause the CRTPGM to fail,

I could replace the UDDS code with DSM but the point of this exercise 
was to demonstrate UDDS.
I have a program that uses DSM here. 
https://wiki.midrange.com/index.php/QDFRTVFD_%E2%80%94_Retrieve_Display_File_Description#DSMFD_Driver
It will be a major rewrite to convert to DSM and probably not worth the 
effort, given the power of SQL, so I may do this only as a spare time 
job, if ever.

RIP UDDS

Regards
Frank Kolmann

On 8/12/2018 9:18 AM, Buck Calabro wrote:
> On 12/7/2018 5:06 PM, Frank Kolmann wrote:
>
> > Looks like my utility will never work on NULL capable fields.
> >
> > --  snip from the RPG Manual ---
> > Database Null Value Support
> > Note: For a program-described file, a null value in the record always
> > causes a data mapping error, regardless of the value specified on the
> > ALWNULL keyword.
> > ---- end snip  ----
> Perhaps I can read the mapping error *DIAG messages and infer that the
> columns are NULL. The question is whether the rest of the columns will
> get populated or not.
> --buck
>
> http://wiki.midrange.com
> Your updates make it better!