Delete uiprogress object at the end of startup function

Hello,

It seems that MATLAB is not deleting the uiprogress object variable when startup function in App Designer apps ends execution.

• Does it behave differently for some local variables? I do now delete or close (pBar), but why bother when it is local variable?

  function startupFcn(app)
        pBar = Utility.showIndeterminateBar(app.UIFigure);
        %.....        
  end
  %... Still runs....

UPDATE 1

I tested a separate app, and it the correct behaviour operated but not with actual. Though I have tested it with above code, removed the Utility function so that you can test...though there is nothing...

UPDATE 2

Tested with onCleanup, the result is the same...I can conclude that this has to do with MATLAB not clearing the startupFcn on time/immediately...The question would be; is there anything that can be done to prevent this?

  function onCleanUpTask = showIndeterminateBar(uifigObj)
        uiprogbar = uiprogressdlg(uifigObj,'Title','Please Wait...',"Indeterminate","on");
        onCleanUpTask = onCleanup(@()delete(uiprogbar));
  end

For your full knowledge I do have:

  app.onCleanupArray{1} = onCleanup(@()cleanUpTasks(ParamNumberIn));

ParamNumberIn is a param variable local to startupFcn which will be deleted when the UIFigure is deleted. Which maybe the cause that MATLAB is saving the WORKSPACE for that function because this referenced local variable?

[Adam Danz]

Just a shot in the dark, but what if you execute this at the end of the startupFcn?

delete(pBar)

[Bereketab Gulai]

Even if one was to execute this at the end of the startupFcn, then it should be deleted/cleared. I suppose, unless it was a global variable like:

app.pBar = ...

Here is the reference is saved.

[Adam Danz]

What is this and where did it come from?

Utility.showIndeterminateBar

[Bereketab Gulai]

Yes, I have explained the problem in detail now. But the function is just a cover.

[Adam Danz]

I assumed that the progress bar you're describing is produced in Utility.showIndeterminateBar (based on the variable name and that it's called from the startupFcn) but I don't know what that function is.

AppDesigner doesn't show a progress bar when opening the app unless you've programmed one, so the source of the progress bar is unclear.

When opening the app for editing, a progress bar is shown (example below). Is this was you're referring to?

[Bereketab Gulai]

Sorry,

I meant that

`Utility.showIndeterminateBar`

From my project was a cover function. It just returns uiprogressdlg object and I tested it with the example I have attached it works fine.

Answer 1

[Adam Danz]

The uiprogressdlg outputs a handle to the progress bar. To delete the bar,

d = uiprogressdlg(h); 
delete(d)

to reset it to 0,

d.Value = 0; 

If it works when you use the uiprogressbar directly but it doesn't work when you use your wrapper function, my guess is that you're not providing the correct handle to the uiprogressbar in the output.

When you try to delete it, is there an error?

If the problem persists, please provide the entire wrapper function so we can see what's going on and share any error messages in their entirety.

[Bereketab Gulai]

Hi Adam,

I think that I have understood the problem, MATLAB is saving the WHOLE workspace for that function because there is a referenced local variable, therefore the use of delete/close(pBar) inevitable. But here is the code (read along with the updates in the question):

classdef (Sealed) Utility < handle
    methods (Access = public, Static = true)
        function uiprogbar = showIndeterminateBar(uifigObj)
                uiprogbar = uiprogressdlg(uifigObj,'Title','Please Wait...',"Indeterminate","on");
        end
    end
end

%.... in app....
function startupFcn(app, ParamNumberIn)
        app.onCleanupArray{1} = onCleanup(@()cleanUpTasks(ParamNumberIn));
        
        pBar = Utility.showIndeterminateBar(app.UIFigure);
        
        %.....initialisations....
        
        function cleanUpTasks(numberId)
            % ....do clean up
        end
end

[Adam Danz]

Why not just run uiprogressdlg independently? Why wrap it in another function?

I suggest the following:

1) Set the uiprogbar handle as a private property of your app. To do so, follow step #2 described here.

2) In your startup function, call uiprogressdlg directly. The handle to the progress bar will be stored in the app variable and will be accessible from anywhere within the app where the app variable is accessed.

app.uiprogbar = uiprogressdlg(uifigObj,'Title','Please Wait...',"Indeterminate","on");

3) whenever you want to delete the progress bar,

delete(app.uiprogbar)

[Bereketab Gulai]

Hi Adam,

Thank you for the comment.

1. My project is bigger than one uifigure.
2. There is no point in storing the uiprogressdlg object, since it needs to be deleted and recreated in each use. It cannot be stored as constant or private variable because a running uifigure is required.
3. To meet those conditions, it can be put in a wrapper function and called whenever needed providing the running uifigure handle. This solution works perfectly, the only problem of my discussion was that "the lack of imporance of doing delete(pBar) when the pBar is local to the function thus should be deleted automatically...at the end of the function.".

To conclude, the problem is with that the whole workspace for that function is saved because other variables are referenced. This discussion should probably be moved to "MATLAB support/bug centre", because this rule (Object Lifecycle), I think is not meet for this PARTICULAR variable (pBar) ("No longer referenced anywhere").