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Carrying over variables in app-designer

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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.
  3 Comments
Stephen23
Stephen23 on 13 Sep 2019
Edited: Stephen23 on 13 Sep 2019
"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:
Nom
Nom on 18 Sep 2019
Great link/resource, Thank you!

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Accepted Answer

Adam Danz
Adam Danz on 13 Sep 2019
Edited: Adam Danz on 13 Sep 2019
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
  7 Comments
Prabhakar Vallury
Prabhakar Vallury on 16 Mar 2023
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
Steven Lord on 16 Mar 2023
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')

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