Answered

Prohibit multiple users on Powerapp or SharePoint list

(0) Share

Report

Posted on by Walter

I have a Powerapp that uses a SharePoint list "Books" that holds titles, authors and number of copies of each book. Students can choose just one book and than automatically the number of copies decreases with one copy. If the number of copies of a certain book has become 0 (zero) than the book disappears from the gallery where I show the SharePoint list in.

Now since multiple students can have access at the same Powerapp at the same time I sometimes end up wth a book showing -3 copies.

f.e. A book has 4 copies and there are 6 students who choose that book at approximately the same moment I end up with -2 copies for that book and the book still shows up in the gallery since the number of copies is not equal to 0.

How can I avoid that I end up with negative saldo of copies, so when the number of copies becomes 0 that book should disappear from the gallery also for users who are watching the app at that moment. I can't find any way.

Maybe I could prevent the use of the powerapp for different users at the same time, so let's say if one students uses the powerapp the other students must wait to open it until the firtst student has chose a book and ended the app. Is that perhaps possible?

Thx a lot for your advice.

Greetz

Walter

Categories:

Building Power Apps

All responses (4)

Answers (1)

Sort by

zmorek 3,272 on at

Like
a
(0)

Report
Copy link

Link copied!

I guess there's a few ways it could be handled, on the OnSubmit property of whatever button you have, perhaps add a Refresh(DataSource) to the top row. Then after that, a simple If() statement could work:

Refresh(DataSource);
If(
LookUp(
DataSource, TitleColumn = ThisItem.Selected.Title, NumberRemainingColumn
) = 0,
Notify("No more books to check out",Error),
[formula to check out book]
)
Walter 71 on at

Like
a
(1)

Report
Copy link

Link copied!

Hi zmorek

Thx a lot for your suggestion. I already tried something likewise before and ok it works perfect for the screen that the student, who has just picked a book, sees. But what about the students who have the same app opened. They don't see the refreshment of the screen, so they still see that a certain book has still one copy although in reality the book has zero copies. So there should be someting possible like...
1. Refresh all screens of other app-copies that are opened by other students
or
2. Prohibit a student to open the app until another student has closed it.

Is there a kind of solution for this.

Thx and greetz

Walter
Verified answer

zmorek 3,272 on at

Like
a
(0)

Report
Copy link

Link copied!

You can also try refreshing the data source with a hidden timer, please see here: https://blog.pragmaticworks.com/how-to-refresh-power-apps-data-sources-on-a-timer#:~:text=This%20is%20where%20the%20timer,and%20auto%20repeat%20that%20timer.

That way, every X seconds that gallery can refresh and reflect an updated amount of books left.
Walter 71 on at

Like
a
(1)

Report
Copy link

Link copied!

Hi zmorek
That did the trick! Thx a lot!! 😊 This communicty rocks! Every day I'm learning from you guys. Very gratefull for all you members and contributors.