Pre-built functions suddenly became undefined in app designer?

In my application I have buttons that are changing color on press by means of code like this:

        function Button_2Pushed(app, event)
            
            app.user_button_sequence = [app.user_button_sequence 2];
            stop(timerfind)
            but2_timer = timer;
            but2_timer.StartDelay = 1;
            but2_timer.StartFcn = @(~,thisEvent) toggleColorOn(app,2);
            but2_timer.TimerFcn = @(~,thisEvent) toggleColorOff(app,2);
            start(but2_timer)

        end

And this has been working perfectly fine as I have been developing it.

I have saved, closed, and opened this many times before, and it was fine each time. Today however, upon trying to make the button change color, it tels me that 'stop' is an undefined function for input arguments of type 'double'. If commented out, it says the same thing about 'start' but for objects (which the timer is).

What happened that this issue is suddenly popping up? I searched for other issues like this and ran into comments about running the code:

        restoredefaultpath
        rehash toolboxcach

but this hasn't fixed anything.

Can anyone share some insight into what happened and why it suddenly stopped working?

Answer 1

[Walter Roberson]

if timerfind() returns empty then it is [] that it returns rather than an empty array of class timer. And stop([]) does not work. You should be using something like

existing_timers = timerfind();
if ~isempty(existing_timers); stop(existing_timers); end

But are you sure you want to stop all other timers and create a new timer, leaving the other ones existing but in stopped state ??

[Thomas Hyatt]

Yes, I need all other timers to stop, though I would rather them not continue existing - so I should probably get around to including a delete function.

But this doesn't explain why

start(but4_timer)

also returns an error saying that 'start' is an undefined function.

The most crazy thing is that I left matlab open for the past couple days, not touching anything while I sought an answer to this question. I am not getting any errors now. What on earth happened? Why was I getting errors before, and why did they suddenly stop happening with literally zero input from me?

I feel like I am going crazy and my computer is possessed.

[Walter Roberson]

You would get the error for start() if somehow timer() returned []

Ideally you should check isempty() on the output of timer -- though it should be rare that timer() returns []... maybe it is possible to run out of timers??

[Jeremy Hughes]

timer should never return [] unless it's been shadowed.

[Jeremy Hughes]

I think Walter is suggesting that there may be other timers, not related to your app, and then calling stop(timerfind) stops things you don't really know about.

We'd have to see the code for but4_timer to know more...

But timer names don't have to be unique, and you can choose them. Then you can use this as a search parameter to only close the timers you are using.

timer('Name','MyTimer'); 
timer('Name','MyTimer');
timer("Name","SomethingElse");
timerfind

ans = 
Timer Object Array

   Index:  ExecutionMode:  Period:  TimerFcn:               Name:
   1       singleShot      1        ''                      MyTimer
   2       singleShot      1        ''                      MyTimer
   3       singleShot      1        ''                      SomethingElse

timerfind("Name","MyTimer")

ans = 
Timer Object Array

   Index:  ExecutionMode:  Period:  TimerFcn:               Name:
   1       singleShot      1        ''                      MyTimer
   2       singleShot      1        ''                      MyTimer

If you don't want them to exist, you should also call delete on the timers you don't want. Otherwise you'll have a bunch of timers hanging around forever. That's probably why your code worked after some time. Some timer was running around.

For additional diagnositcs, try adding a call to "which -all start" and check there's nothing else called timer on the path with "which -all timer"

[Walter Roberson]

@Jeremy Hughes

I had the hypothesis that MATLAB might run out of timers at 2^15 or 2^16, so I decided to test -- and to incidentally plot the time required to create the timers as it went.

The time per timer steadily increases. And the code really crawls, even though I optimized drawing.

At the moment I think my system has only just passed 2^15 after running for a while. (You will probably end up stopping the code, it's just painfully slow to iterate through.)

N = 65536;        %timers to attempt
T = cell(N,1);
times = nan(N,1);

failed = false;

delete(timerfindall);
h = animatedline();

M = 100;         %batch size for plotting
offset_buffer = zeros(M,1);
times_buffer = zeros(M,1);

for K = 1 : N
    time_offset = mod(K-1,M) + 1;
    try
        start = tic;
        thisT = timer();
        stop = toc(start);

        times(K) = stop;
        times_buffer(time_offset) = stop;
        offset_buffer(time_offset) = K;

        if mod(K,M) == 0
            addpoints(h, offset_buffer, times_buffer);
            drawnow();
        end

        if isempty(thisT)
            fprintf('timer empty at %d\n', K);
            failed = true;
            break;
        end
        T{K} = thisT;
    catch ME
        fprintf('timer() fail at %d\n', K);
        failed = true;
    end
end

if time_offset ~= M
    addpoints(h, offset_buffer(1:time_offset), times_buffer(1:time_offset));
    drawnow();
end

if failed
    fprintf('failed\n');
else
    fprintf('succeeded to create %d timers\n', N);
end

[Walter Roberson]

It did eventually end, and does appear to have created all the timers. But timerfind() and timerfindall() are reporting empty even though the timers have ObjectVisibility on

[Jeremy Hughes]

Thanks @Walter Roberson, This is a great analysis. There's no hard limit on the number of timers, but it looks like you've hit the practical limits of how many you can create.

I'm surprised timerfind doesn't return anything. I'll look at that one.