App Desinger: How to access Labels/Spinners via "Tags" in a custom UI component?

I have a modularized App Designer app with several custom UI components. One UI component is a setting for units (e.g. km/h - mph or deg - radiant). These settings should be applied to all other custom UI components. To reduce the implementation work I wan't a generic solution like:

1. User changed the setting from "rad" toi "deg"
2. all custom UI components get notified and get the changed data
3. in the components should be a function with updates all Labels tagged with "LabelUnitAngle" from "rad" to "deg"

The non-generic solution is already working: comp.WheelAngleunitLabel.Text=comp.appSettings.units.angle.text;

comp.WheelAngleSpinner.Value = comp.ParamStore.WheelAngle*comp.appSettings.units.angle.factor;

I tried findall and findobj and tried using metaclasses but still no luck.

[dpb]

It would undoubtedly help if you could post the startup code section that creates the components in question.

Can you find the app uifigure itself programmatically, first, just for starters?

Have you tried passing the UIFigure handle as the object tree starting point in findall(), etc., ...?

[Walter]

Thanks @dpb that you would like to help me. Without a meta class it was not possible for me. I finally found a solution:

function updateElementsByTags(comp)
%UPDATEELEMENTSBYTAGS  Update UI labels in this component based on Tag values.
%
%   This method scans all private, transient, non-copyable graphics
%   properties of the component and updates their Text property
%   depending on the Tag value. The unit strings are taken from
%   comp.appSettings.units.*.text.

    % Get only the UI handles (graphics objects); we ignore the names here
    [~, handles] = getPrivateUiComponents(comp);

    for k = 1:numel(handles)
        h = handles(k);

        % Safety check: only process objects that actually have Tag and Text
        if ~isprop(h, "Tag") || ~isprop(h, "Text")
            continue;
        end

        % Use the Tag to decide which unit text to apply
        switch string(h.Tag)
            case "TagUnitAngle"
                h.Text = comp.appSettings.units.angle.text;

            case "TagUnitVelocity"
                h.Text = comp.appSettings.units.velocity.text;

            case "TagUnitYawRate"
                h.Text = comp.appSettings.units.yawrate.text;

            case "TagUnitLength"
                h.Text = comp.appSettings.units.length.text;

            case "TagUnitAcceleration"
                h.Text = comp.appSettings.units.acceleration.text;

            otherwise
                % Ignore all other tags
        end
    end


    function [names, handles] = getPrivateUiComponents(obj)
        %GETPRIVATEUICOMPONENTS Return private transient graphics properties.
        %
        %   [NAMES, HANDLES] = GETPRIVATEUICOMPONENTS(OBJ) inspects the
        %   metaclass of OBJ, selects properties that are:
        %       - private
        %       - Transient
        %       - NonCopyable
        %       - not Constant
        %       - not Dependent
        %
        %   For each of these properties, the current value is read. If the
        %   value is a graphics object (or array of graphics objects),
        %   they are collected into HANDLES. NAMES returns the corresponding
        %   property names.

        % Get metaclass information
        mc    = metaclass(obj);
        plist = mc.PropertyList;   % array of matlab.metadata.Property objects

        % Select only UI-related properties based on their metadata
        isUiProp = arrayfun(@(p) ...
            strcmp(p.GetAccess, "private") && ...
            p.Transient && ...
            p.NonCopyable && ...
            ~p.Constant && ...
            ~p.Dependent, ...
            plist);

        plist = plist(isUiProp);

        % Collect names
        names   = {plist.Name};

        % Initialize empty array of graphics handles
        handles = gobjects(0);

        % Read property values and keep only graphics objects
        for k = 1:numel(names)
            v = obj.(names{k});

            % v may be a scalar handle, an array of handles, or something else
            if isgraphics(v)
                % Ensure we treat v as a column vector of handles
                handles(end+1:end+numel(v)) = v(:); %#ok<AGROW>
            end
        end
    end

end

Answer 1

[Mario Malic]

Just thinking out here, wouldn't you want an each component to have an internal method that changes values/labels/anything that relates to the selected unit?

Create an event in your main component and make it trigger when the unit is changed (user interaction). Subscribe your other components to it and fire up the internal event to change units.

https://nl.mathworks.com/help/matlab/matlab_oop/learning-to-use-events-and-listeners.html

[Image Analyst]

Excellent solution. 🤔

[Mario Malic]

thanks! 😊