uiputfile blocks all of MatLab any error it keeps repeating, it requires CTR-ALT-DEL end task (my app) to exit

I wrote this code that ends up being an endless loop Due to weird treatment of this particular dialog

I can't add a breakpoint while (Save to) is open looking for a path from the call uiputfile(...

Code that I think should run fine is in an endless loop that can't be exited since all of MatLab all is locked out.

Even after CTR-ALT-DEL End task the dialog stays open, but at least with no calling app I can finally close it.

No Ctrl-C allowed anywhere, No response from Command Window, App Designer or my app itself, just endless beeps and reopening the dialog. Neither OK or cancel gets out of it but in the example below Cancel with throw an erro so you won't have my problem

Try this (modified code, removing app.propertied to work in your command window

The goal is to exit the while with a valid path (app.)OutLoc

startingFolder = "";
baseFileName = '*.csv';
OutLoc = "";  % Must use "" as isfolder thinks " " is a folder!
while ~isfolder(OutLoc) % Let's stay here until it's good
    defaultFileName = fullfile(startingFolder,baseFileName);
    % Show all files in the folder by using "*.*"
    [baseFileName, startingFolder] = uiputfile('*.*',  ...
        'Save to', defaultFileName); 
    % Various ways of chacking throw wrong type errors so I settled on this    
    if size(baseFileName,2)<6  % Is baseFileName any good (or even a string)?
        % User clicked the Cancel button. or didn't enter a file
        uialert(app.MouseOdor,"No file name given","No Output File"); % Crash when not running it app
    end 
    if ~isstring(startingFolder)  % because uiputfile() will change it to 0 on cancel
        startingFolder = "";
    end
    if isfolder(startingFolder)
        OutLoc = startingFolder; % All good, should exit the loop now
        MouseFolder  = startingFolder;   % actually saving it to app.MouseFolder.Value for later use
    end
end % while

Error using uiputfile (line 102)
Support for Java user interfaces is required, which is not available on this platform.

I tried running it in here, so now I know it's a Java issue... lovely.

I guess you will have to copy and paste it to your command window and try yourself.

BTW, I'm in 2023b, probably time to upgrade

Also, when I ask a question like the above does Ask the Community page not allow any text into the Description* block.

How does it decide it doesn't like my question?

[Gavin]

Running with the debugger already started I see the problem is

[baseFileName, startingFolder] = uiputfile('*.*', ...

'Save to', defaultFileName);

Doesn't fill in startingFolder it's still empty if I give a file name with no extension.

I didn't want .ext since I' really just looking for the directory path I don't care about the full file name as it will be changed as there sill be multiple output files placed here with different extensions.

SO... Workaround is to use some dummy extension like .csv or .txt and change it later.

AND even if I get this right by adding an extension isstring() fails since apparently the returned file name string is a char

change ~isstring(...) to ~ischar(...) and it finally works. For an untyped language m sure can be picky!

Still the issue exists and several things should be fixed.

[Walter Roberson]

Doesn't fill in startingFolder it's still empty if I give a file name with no extension.

I am not able to replicate that behaviour with R2024b for MacOS Intel

[dpb]

"...the goal is to exit the while with a valid path (app.)OutLoc"

%...
%OutLoc = "";  % Must use "" as isfolder thinks " " is a folder!
%while ~isfolder(OutLoc) % Let's stay here until it's good
%...

I hadn't ever tried that, but I would submit that

isfolder(' ')

returning True is a bug and should be reported as such unless on Linux and there actually is a folder with " " as its name (allowable, but not necessarily wise). Converting it back to the empty string will be the cause of the infinite loop.

The comment above about "~isstring() was a first thought I had -- the doc says the output path is a char() vector while the filename can be either a string or a char() vector (what cause which isn't described; that's a deficiency in the doc) but I'd suggest using

while ~(exist(OutLoc)==7)

as more robust given the above behavior of isfolder()

Also, if the only point is to set an output directory for writing into, why not use uigetdir?

[Govind KM]

@dpb,

isfolder(' ')

returning True seems to be expected behaviour:

https://www.mathworks.com/matlabcentral/answers/502230-why-does-isfolder-returns-true-when-the-argument-is-a-space-character-in-windows-os

[Swastik Sarkar]

Hi @Gavin,

Doesn't fill in startingFolder it's still empty if I give a file name with no extension.

I've tested this on MATLAB R2023b on both Windows and Debian 12 (Linux), but I haven't been able to reproduce the problem.

It would be helpful to have the code for the app to determine if the issue can be replicated.

[dpb]

input = " ";
input = fl::filesystem::absolute(input)

Invalid use of operator.

The example in the linked-to Answer doesn't work under R2021b.

I suppose one can make the argument they do that

isfolder(fn)

is evaluated as

isfolder(trim(fn))

but it's still imo unexpected behavior in MATLAB since a blank folder can't exist under Windows...

No way one will change TMW's mind on this one, however, so best one could do would be to ask for a note to be added to the documentation regarding that behavior. And, of course, it is true for all related functions, not just isfolder

Answer 1

[Gavin]

I changed from uiputfile() to uigetdir(startingFolder... as that is what I was really looking for: Where will the output files go. In App Designer uiputfile('*.*', ... Where the user input is a name with no extension it fails in MATLAB. But using uiputfile('*.csv', ... where, I guess Windoze fills in the extension, keeps MATLAB happy. So the issue is that uiputfile in App Designer MATLAB program can't handle a file with no extension.

Yes, wasn't the best code for what I needed but it should have worked and my alternative does, so I'm able to move on.

[dpb]

" uiputfile in App Designer MATLAB program can't handle a file with no extension"

Note that App Designer has no bearing on the behavior of base MATLAB functions; they operate the same whether in or outside the graphical interface.

I don't see any failure in uiputfile with a returned name from the user with no extension --

>> [f,d,ix]=uiputfile('*.*')
f =
    'foobar'
d =
    'C:\Temp\'
ix =
     1
>> 

The returned filename is that typed in; the directory is the current working directory at the time the call is made if not given explicitly.

The problem in your code was mostly centered about the loop never terminating because the logic of changing the pertinent flag variable kept resetting it because of the test on the type of the returned variable always failing because uiputfile doesn't return a string but a char() vector.

If you change directories in the call, then, it returns the new changed-to directory...

>> defaultFile=fullfile('*')        % no extension, directory again
defaultFile =
    '*'
>> pwd                              % show where we are when run first...
ans =
    'C:\Temp'
>> [f,d]=uiputfile('*.*','Save To',defaultFile)
f =
    'NewName'
d =
    'C:\Users\DPB\Documents\MATLAB\Work\'
>> 

Again, works as expected; nothing really required except to call it and parse the result; branching if the user cancels and the return filename and folder are numeric instead of character vectors.

>> [f,d]=uiputfile('*.*','Save To',defaultFile)
f =
     0
d =
     0
> assert(~isnumeric(f),'User Canceled')
User Canceled 
>>