Function 'subsindex' is not defined for values of class 'matlab.gr​aphics.Gra​phicsPlace​holder'

I have the following Figure

classdef gui < matlab.apps.AppBase
   ...
     function app = gui
        % Construct app
     end
   ...
   properties (Access = public)
     myFuncRef = @myFun
   end
   ...
   function myFun(app)
      % do something
   end
   ...
end

in which I have defined the method

myFun

If the Figure is running, that is it's showing a window, how can I invoke the method "MyFun" from the Command Window of MATLAB or MATLAB Fcn Block in Simulink ? In the simulink I tried with

   h = findobj(0, 'type', 'figure');
    funcRef = get(h, 'myFuncRef');
    funcRef(h);

but I get the error

An error occurred while running the simulation and the simulation was terminated Caused by: Function 'subsindex' is not defined for values of class 'matlab.graphics.GraphicsPlaceholder'.

Thanks in advance!

Answer 1

[Bob Blaine]

Hi tahec,

The error message is telling you that findobj didn't find any figures on the graphics root, and couldn't resolve the function call. If you open MATLAB with no graphics and just execute your "h = ..." block of code you will get that error.

AppBase is the base class for an App Designer application and usually contains a UIFigure, which is what shows up on the screen. Even if you are creating a UIFigure in the constructor, it won't show up in a findobj, but it will show up in findall:

h = findall(0,'type', 'figure')

That will get you halfway there. One other thing you will have to do is put a handle to the gui object in the UIFigure's UserData property. You can then call its function:

if ~isempty(h) then
  h.UserData.myFun()
end

Having said all of this, I'm hoping that this is for debugging, or fiddling with a parameter. You'd probably want to code something into the graphics GUI as a permanent functionality.

[tahec]

Hi Bob, thank you very much for your reply! I have a doubt. Could you explain me how to "put a handle to the gui object in the UIFigure's UserData property" ?

You'd probably want to code something into the graphics GUI as a permanent functionality.

Exactly.

[Bob Blaine]

Hi tahec,

Sorry about being a little vague, but based on the code you posted, I was assuming that you were constructing the UIFigure in the constructor of your gui object the way App Designer does:

classdef MyObject < matlab.apps.AppBase
    properties
        UIFigure matlab.ui.Figure
    end
    methods
        function gui = MyObject
            gui.UIFigure = matlab.ui.Figure;
            % Set the Userdata on the UIFigure to gui
            gui.UIFigure.UserData = gui;
        end
    end
end

If you aren't creating a UIFigure, then I'm not sure where you can get a handle to your gui object. That may require someone more Simulink savvy to help you out.

[tahec]

Hi Bob,

I show you what I did.

This is the class

classdef gui < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        AlternatingControllersUIFigure  matlab.ui.Figure
        f_ref = @f;
        ...
    end

    methods (Access = private)
        function f(app)
           ...
        end

        % Code that executes after component creation
        function startupFcn(app)
           app.AlternatingControllersUIFigure.UserData = app;
        end

        % Create UIFigure and components
        function createComponents(app)
            app.AlternatingControllersUIFigure = uifigure;
            ...
        end
    end

    methods (Access = public)

        % Construct app
        function app = gui

            % Create and configure components
            createComponents(app)

            % Register the app with App Designer
            registerApp(app, app.AlternatingControllersUIFigure)

            % Execute the startup function
            runStartupFcn(app, @startupFcn)

            if nargout == 0
                clear app
            end
        end
    end
end

In the block diagram, I have the following block

in which I wrote the following code

When I run the overall app (gui + block diagram), simulink tells me

What is the matter? Note that I am not obligated to use the block "MATLAB Function".