Why is event PreUpdate and PostUpdate not triggered in ChartContainer?

Hi all,

I’ve created a ChartContainer in MATLAB R2024b and need to track when its update routine finishes so I can restore an internal property to its original value. During setup, I added listeners for the PreUpdate and PostUpdate events of the ChartContainer.

However, when I change a property, the update method runs, but neither the PreUpdate nor PostUpdate events seem to fire.

Below I share the class implementation:

classdef TestComponent < matlab.graphics.chartcontainer.ChartContainer
    
    %% Properties
    properties (AbortSet)

        % Internal use. Indicates update is required, triggered by external
        % property.
        TriggerUpdate (1,1) logical = false;

    end %properties

    properties (Transient, NonCopyable, Hidden, SetAccess = protected, UsedInUpdate = false)

        % Event listener array
        EventListeners (1,:) event.listener

    end
    
    %% Protected Methods
    methods (Access = protected)

        function setup(obj)
            % Setup routine

            % Show setup routine is executed
            disp('setup')

            % Setup listeners to all events in the class
            metaClass = meta.class.fromName(class(obj));
            eventList = {metaClass.EventList.Name};
            listenAcces = {metaClass.EventList.ListenAccess};

            % Initialize listener to post-update event
            for idx = 1:numel(eventList)
                if ~strcmpi(listenAcces{idx}, {'public', 'protected'})
                    continue
                end
                obj.EventListeners(end+1) = listener(obj, ...
                    eventList{idx}, @(s,e) obj.showEvent(e));
            end
        end %function
        
        function update(obj)
            % Update routine

            % Show update routine is executed
            disp('update')
        end %function

    end %methods

    methods

        function showEvent(obj, e)
            disp(e)
        end %function

    end %methods
end

Does anyone know why these events aren’t triggered? For ComponentContainer, the events work as expected.

Answer 1

[Aditya]

Hi Jacob,

You have observed correctly: PreUpdate and PostUpdate events are available and documented for ComponentContainer (UI components), but not for ChartContainer (axes-based charts).Why aren't PreUpdate/PostUpdate firing in ChartContainer?

• ChartContainer does not define or fire PreUpdate/PostUpdate events.
• The MATLAB documentation for ComponentContainer explicitly lists these events, but the ChartContainer documentation does not.
• This is by design: ChartContainer update cycle is not evented in the same way as ComponentContainer.

You can try the following steps:

• Override the update method and place your logic before and after calling the superclass update, if needed.
• If you need to execute code after every update, do it at the end of your update method.
• If you have code that should run before an update, do it at the beginning of update.