check if mainAPP exist in app designer

hi, i read this guide :

https://it.mathworks.com/help/matlab/creating_guis/creating-multiwindow-apps-in-app-designer.html

i want to know if Main App has been launched.. otherwise I launch it from here

[chrisw23]

Typically the main app starts a child app and hold its app instance. If the main app will be closed the child app should be closed too by the close callback.

properties (Access = private)
 childApp    % declare  private property
end

...
app.childApp = ChildApp(<arg>) % start child app somewhere
...

function CloseRequest(app)
   app.childApp.delete      % close the child app first
   app.delete               % close the main app   
end

[piero]

Yes, that's correct, but I didn't ask it

I want to know from within childApp if the main exists (because when I develop the child app I can't always run the main to test the child it takes longer)

[chrisw23]

Sry, but you mentioned that you have to start your main anyway. If it's not yet open "... otherwise I launch it from here"

[chrisw23]

Since Matlab R2020 you have the option to set the 'Single Running Instance' flag. Maybe this is a workaround for your problem.

Manage Code in App Designer Code View - MATLAB & Simulink - MathWorks Deutschland

"When Single Running Instance is selected and you run the app multiple times, MATLAB reuses the existing instance and brings it to the front rather than creating a new one. When this option is cleared, MATLAB creates a new app instance each time you run it and continues to run the existing instances. These run behaviors apply to apps that you run from the Apps tab on the MATLAB Toolstrip or from the Command Window.

When you run apps from App Designer their behavior doesn't change whether this option is selected or cleared. App Designer always closes the existing app instance before creating a new one."

[piero]

thanks

Answer 1

[Walter Roberson]

No. MATLAB does not offer any any general mechanism to test whether variables of particular classes exist.

[piero]

i created 2 tables in app designer The MAIN table A and the child table B inheriting data from A via input into the function

Question: when I develop table B as there are variables passed as a parameter of A how do I do the various tests on B without launching A? the development phase of B becomes very difficult that I have to launch table A all the time