How to handle listener lifetime in MATLAB apps?

This simple two-window app has a data source app which passes data via an event to one or more listeners. The source is waveformMaker_01.mlapp and receiver(s) xyPlotter_01.mlapp.

Q1) I am principally concerned with the lifetime of the event.listeners.

At present I store these in the receiver and delete them with the receiver's <mainUIFigure>CloseRequest() callback. But the ...CloseRequest() callback is not called when the receiver is simply delete()-ed, which leaves the event.listeners extant but invalid. For now I can call close( <receiver>.<mainUIFigure>) but the principle that destructors must properly close resources when objects go out of scope is broken.

Is there a better way to control the lifetime of the event.listeners?

Q2) There is a choice to either send data in a custom EventData class or to poll the source for the next chunk of data. Which method is preferred? (I recognise that my AnyEventData class is a kludge.)

Q3) Any other code review comments?

Answer 1

[RST]

Answering my own question.

I have not tried MagicListener for this, but it looks useful.

Instead, my client app

• saves a list of listeners that link to it.
• listens its ObjectBeingDeleted event, as this is more consistent than the CloseRequest callback
• deletes the listeners within its ObjectBeingDeletedCallback

as per this code snippet

    properties (Access = private)
        listenerList (1,:) event.listener
    end
    
    methods (Access = public)
        
        .
        .
        .
        function sourceChangedCallback( app, src, evdata )
            % do useful things...
        end
        
        function addSourceChangedListener( app, src, eventName )
            app.listenerList(end+1) = addlistener(src, eventName, @app.sourceChangedCallback);
        end
        
     
    end
    
    methods( Access = private)
        function beingDestroyedCallback( app, src, evdata ) %#ok<INUSD> 
            app.deleteListeners();    
        end
        
        function deleteListeners( app )
            delete( app.listenerList );
            app.listenerList = event.listener.empty();
        end
    end
    
    .
    .
    .
    
    % Code that executes after component creation
    function startupFcn(app)
          
        addlistener(app, 'ObjectBeingDestroyed', ...
                         @app.beingDestroyedCallback);
                
    end