How to assign a callback to a gui element created at runtime

Hi,

In AppDesigner I created an app that creates a slider at runtime:

Tt_end_slider = uislider();
Tt_end_slider.Position = app.emptySlider_2.Position;
Tt_end_slider.Tag='t_end';
Tt_end_slider.UserData=i;
Tt_end_slider.ValueChangedFcn = @(source, event) app.osc_prev_slider_ValueChanged ;

The Callback is defined as follows

  % Callback function
        function osc_prev_slider_ValueChanged(app, event)
            value = event.Source.Value;
[..]
        end
        

Using the slider, I get this error:

Not enough input arguments.

Error in tutorialApp/osc_prev_slider_ValueChanged (line 575)

value = event.Source.Value;

Error in tutorialApp>@(source,event)app.osc_prev_slider_ValueChanged (line 325)

Tt_start_slider(i).ValueChangedFcn = @(source,event)app.osc_prev_slider_ValueChanged ;

I couldn't find how to correctly pass the requested argument to the callback ( I tried with @(source,event) looking at the callbacks assigned using the graphic interface)

Answer 1

[Cris LaPierre]

You're close. I see two errors.

1. "Not enough input arguments" is because you are not passing 2 inputs to your callback function. App Designer automatically passes app, but you need to pass in something for event. Update your ValueChangedFcn to this

Tt_end_slider.ValueChangedFcn = @(source, event) app.osc_prev_slider_ValueChanged(Tt_end_slider);

2. Inside your callback function, you are using incorrect dot notation to get the value of the slider. Remove ".Source".

value = event.Value;

[Ilario Triscari]

Thank you, now it works. However I did not understand the difference between arguments in the first parenthesis and arguments in the second one.