In Matlab app When I delete a Editfieldnumeric component and delete it the call back function remains and when I next create a new component I do not see the callback

In one Matlab App I created a EditFieldNUmeric component and later deleted it. But the call back function remains.Why?

Also later I inserted a EditField numeric component ,I did not get the new callback function.Why?

Also please let me know how to use the numeric value in the call back function of another component

Answer 1

[Garmit Pant]

Hello Ashok,

When you create a component in MATLAB App Designer and later delete it, the callback function associated with that component may not automatically be removed from the code. This is why the callback function remains even after you delete the component.

Why the Callback Function Remains

• Manual Removal: When you delete a component, MATLAB does not automatically remove the associated callback functions. You need to manually remove the callback function code from your app.
• Code Consistency: MATLAB assumes that you might still need the callback function for some other purpose or might want to reassign it to another component.

When you insert a new ‘EditField’ numeric component, MATLAB does not automatically generate a new callback function if there is already an existing callback function with the same name. You need to manually assign or create a new callback function for the new component.

To use the numeric value in another function in the app, you need to store the value as a property. Please follow these steps to add a new property and change its value during a callback:

1. Define a Property: Define a property in your app to store the numeric value.
2. Update the Property: Update this property in the callback function of the ‘EditField’ numeric component.
3. Access the Stored Value: Access the stored value in the callback function of another component.

Here is a code snippet that highlights how to add a new property, change its value, and use it in another callback:

classdef MyApp < matlab.apps.AppBase

    % Properties that correspond to app components
    properties (Access = public)
        UIFigure          matlab.ui.Figure
        EditFieldNumeric  matlab.ui.control.NumericEditField
        AnotherComponent  matlab.ui.control.Button
    end

    properties (Access = private)
        NumericValue % Property to store the numeric value
    end

    % Callbacks that handle component events
    methods (Access = private)

        % Value changed function: EditFieldNumeric
        function EditFieldNumericValueChanged(app, event)
            app.NumericValue = app.EditFieldNumeric.Value;
        end

        % Button pushed function: AnotherComponent
        function AnotherComponentPushed(app, event)
            % Use the numeric value stored in the property
            disp(['The numeric value is: ', num2str(app.NumericValue)]);
        end
    end

    % Component initialization and other functionalities below
   

For further understanding, kindly refer to the following MathWorks Documentation:

• Refer to the ‘Delete Callbacks’ section: https://www.mathworks.com/help/matlab/creating_guis/write-callbacks-for-gui-in-app-designer.html#mw_7217c6ec-0ad0-4190-b2d9-f9104cbb8805

I hope you find the above explanation and suggestions useful!

[Ashok]

Thanks for the detailed answer. I will try this out

[Garmit Pant]

@Ashok if you find the answer helpful, consider accepting. Feel free to further inquire as well.