In the world of green-screen programming, one basic function a program has is dealing with information that the user enters on the screen, including changes to data.
On a simple screen, processing user-entered changes can be straightforward--editing, validating, and then processing. On more sophisticated screens, it is not as straightforward.
In my position, I write many subfile programs. In any program, I can give the user several options for positioning and filtering the subfile. I may also give the user Option 1=Add lines. These functions usually involve validation and rebuilding the subfile.
So why should I check what the user enters on the screen? If the data hasn't changed from the last time the user pressed Enter (or another function key), I really don't want to re-validate the data or rebuild the subfile. That would be redundant.
One way to check for changes in screen data is to use the CHANGE keyword for display file DDS. The syntax is CHANGE(nn), where nn is an indicator. This can be a record-level keyword to apply to all input-capable fields in the format, or it can be a field-level keyword. If the user types into a field that is affected by this keyword, then indicator nn is set on.
All your program needs to do is check that indicator to see if the data in the field has changed.
OK. Whoa. Back up the iSeries delivery truck. That last statement is not entirely accurate. CHANGE sets on the indicator if the user has typed into the field. That does not mean that the data in the field has changed. The user could type into a blank field and then blank out the field again. Or the user could type in a new value for the field, change his mind, and type in the original value again.
This doesn't work for me. If the user does something like this, and the indicator comes back to my program set on, I could end up rebuilding my subfile when I don't really need to (possibly confusing the user in the process). Or I could do a validation routine again when it is not needed--not good if the routine is extensive and/or I/O intensive.
So I rarely use CHANGE. I've come up with a different approach to see if screen data actually changes.
I keep a list of fields I want to check for user-entered change in my RPG program. Here's an example:
D S1 DS
D S1WO
D S1WO2
D S1NO
D S1DESC
D S1LOCATION
D S1REQLOC
D S1@WO // Option 1=Add fields...
D S1@NO
D S1@DESC
D P1 S like(S1)
The data structure S1 lists all the fields from my screen format that I want to check. It will contain the values of the fields from the last read of the screen. Note the field P1, which is defined like S1. This will contain the previous values of the screen fields. It is fine as a standalone field for the most part. Defining it with LIKEDS can also be useful if I need to check for changes in individual fields.
I also have some switches:
D |
D ChgFound N
D ForceChg N inz(*off)
ChgFound will be set on if any of the fields have had data changed. I use ForceChg if I want to make the program think there is a screen data change, regardless if there is any or not. I often use ForceChg when my program is changing screen data itself, such as in F5=Refresh processing.
Now, here's the main screen processing routine:
begsr $Screen1;
// Main Screen
// ================================================================
exsr $Show;
|
|
|
if CmdKey = F5;
exsr $ClrAdd;
ForceChg = TRUE;
endif;
exsr $ScreenChange;
if ErrFound OR ChgFound;
exsr $Edit;
if ErrFound;
leavesr;
endif;
endif;
|
|
|
exsr $Process;
endsr;
First, the F5=Refresh processing forces a change. Since I'm refreshing, I may be changing screen data myself (clearing out subfile filter or position-to fields or Option 1=Add fields, for example), and I would need to rebuild the subfile.
Then, I execute a routine to check for screen changes, using the list defined earlier:
begsr $ScreenChange;
// ================================================================
ChgFound = ForceChg OR (S1 <> P1);
ForceChg = FALSE;
P1 = S1;
endsr;
If there is a change (actual or forced), ChgFound is set on.
Now, if the user did make a change (or there are still errors from the last time the validation routine $Edit was run), the edit routine $Edit is run.
begsr $S1Edit;
// ================================================================
ErrFound = FALSE;
inError = *ALL'0';
dou Once;
// Edits go here
enddo;
// --------------------------------
ErrFound = (inError <> *ALL'0');
exsr $Clear;
if NOT ErrFound;
exsr $Load;
endif;
endsr;
This is the routine that validates the user-entered data and rebuilds the subfile. And it is run only when the user actually changes data on the screen (or a change is forced).
This is a relatively simple technique for checking if data coming in from a screen has actually been changed, rather than using CHANGE, which merely tells if a field has been typed into. You may use this technique, or, ahem, change it as you see fit.
Doug Eckersley is the chief iSeries developer at Dominion Homes in Dublin, Ohio. He has over 16 years of application development experience. He is the co-author of Brainbench’s RPG IV certification test. This year, his family is hosting a boy from Germany, while supporting their Hong Kong boy through his sophomore year at the University of Dayton.
More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.
TRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now! Request Now.
Forms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.
Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:
Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.
IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn:
LATEST COMMENTS
MC Press Online