Carrying over variables in app-designer

I have a script which searches for strings in files located in a folder.

I have a GUI made from appdesigner which has a button for where to pick your folder as well as where to pick your output file (to dump the gathered data to)

However, it is not letting me carry over variables from one function to another in the app designer's code view.

I have three buttons:

First one to open the folder you want to search in

        % Button pushed function: FoldertoSearchButton
function FoldertoSearchButtonPushed(app, event)
            fileLoc = uigetdir;
end

Second to choose the output file

  % Button pushed function: FileButton
        function FileButtonPushed(app, event)
           outputFile = uigetfile('*.xls*');    
        end

and third to output the rejected file (ones which failed to have the given user-defined string in them):\

           % Button pushed function: FileButton_2
        function FileButton_2Pushed(app, event)
           rejectFile = uigetfile('*.xls*');
        end
    end

I then have function located on the Start button callback which initializes the script.

       % Button pushed function: StartButton
        function StartButtonPushed(app, event)
            stmFileSearch(app,fileLoc,outputFile,rejectFile)

        end

The problem I'm having is it's giving me errors such as fileLoc is not defined, even when I have in the first button.

[Nom]

This problem was solved by using global variables

so in this case defining

          global fileLoc 
          fileLoc = uigetdir;

in the respective buttons and then calling the global variable in the StartButton

            global fileLoc 
            global outputFile
            global  rejectFile
            stmFileSearch(app,fileLoc,outputFile,rejectFile)

This is definitely not the preferred way of solving this problem, but it works.

If anyone else has any better alternatives, I would love to learn.

[Stephen23]

"This is definitely not the preferred way of solving this problem"

Very true.

If anyone else has any better alternatives, I would love to learn.

Tthe MATLAB documentation is the best place to learn how MATLAB works:

https://www.mathworks.com/help/matlab/creating_guis/share-data-across-callbacks-in-app-designer.html

[Nom]

Great link/resource, Thank you!

Answer 1

[Adam Danz]

Avoid using global variables.

Instead, you can define a new property of your app that stores the fileLoc data. The process is explained here but I'll summarize what you need to do below.

1. From the editor tab in App Designer, select the red "Property" dropdown button at the top and select "Private Property". This will add a property definition to a properties block.
2. Within that newly added section, you can define any variable name that will store your fileLoc data (see section 1 below).
3. In your FoldertoSearchButtonPushed() function, save the fileLoc to the app (see section 2 below).
4. Now you can access the fileLoc property anywhere within your gui (see section 3 below).

% Section 1
properties (Access = private)
    fileLoc = ''; % Directory chosen by user in FoldertoSearchButtonPushed()
end
    
% Section 2
function FoldertoSearchButtonPushed(app, event)
    fileLoc = uigetdir;
    app.fileLoc = fileLoc; 
end

% Section 3
function StartButtonPushed(app, event)
    stmFileSearch(app,app.fileLoc,outputFile,rejectFile)
    %                 ^^^^^^^^^^^
end

[Nom]

Thank you Adam,

I will implement this and give it a go as soon as I can, I love learning the proper way of doing this!

Thank you!

[Adam Danz]

Glad I could help!

[Nom]

Perfect!

Just implemented it and it works flawlessly.

One small change I had to make (due to an error)

was just in section 2:

% Section 2
function FoldertoSearchButtonPushed(app, event)
    app.fileLoc = uigetdir;
end

Just had to remove the two lines and replace it with

app.fileLoc = uigetdir;

It acomplishes the same thing, I love it!

[Adam Danz]

Thanks for the feedback! Currious, what was the error, if you recall?

[Nom]

My apologises, it wasn't an error par se , however it kept recommending me to change it to

                app.fileLoc = uigetdir;
                app.fileLoc = app.fileLoc; 

At which I thought to just changed it to

                app.fileLoc = uigetdir;

This change made no differece for the rest of my code when I called back to it using

app.fileLoc

[Prabhakar Vallury]

I'm having similar problems with global variables and tried the above. One big problem I face is that I need to save these property variables into a .mat file. Using the above example,

save ('file1.mat', 'app.fileLoc') comes back with an error saying it's not a valid variable. Almost there, would appreciate any help from this group. TMIA.

Joe

[Steven Lord]

The save function requires variable names not expressions when indicating what subset of data in the workspace to save. 'app.fileLoc' is an expression. Store the value of that property to a local variable in the function where you want to call save then save that local variable.

theFile = app.fileLoc;
save('file1.mat', 'theFile')