Listener doesnt display messages after changes through workspace

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Hello, I tried to practice with event and listener objects.
As I practiced, I made two classes, one with an event and one with a listener function upon the event.
I noticed that the listener doesnt display messages if the event is trigerred through the workspace.
The event code:
classdef EventPractice < handle
properties (SetObservable = true)
NumEvent = 1
end
events
NumChangedEvent
end
methods
function set.NumEvent(obj,value)
obj.NumEvent = value;
notify(obj,'NumChangedEvent');
end
end
end
The listener code:
classdef ListenerPractice < handle
properties
NumListener = 1
end
methods
function obj = ListenerPractice(EventSrc)
addlistener(EventSrc,'NumChangedEvent',@obj.ListenerReaction);
end
end
methods
function ListenerReaction(obj,EventSrc,~)
obj.NumListener = EventSrc.NumEvent
disp(['The event Num has changed. The listener Num changes to the same num: 'num2str(EventSrc.NumEvent)])
end
end
end
Creation Code:
EventExample = EventPractice;
ListenerExample = ListenerPractice(EventExample);
Change at the Workspace:
Change reaction at the ListenerExample variable:
Empty Command Window:
After this whole process, If the NumListener variable changed at the listener function 'ListenerReaction', why didnt the disp() function also go into action?
Thank you for reading,
Yuval Blutman.
  4 Comments
Yuval Blutman
Yuval Blutman on 17 Dec 2022
Hello, about the set.NumEvent function, it does work in my end. And for the missing comma or space, It is indeed missing and probably got cut as i copied the code. I will add here the code files themselves and this is the actual code line:
disp(['The event Num has changed. The listener Num changes to the same num: ' num2str(EventSrc.NumEvent)])
I also emphasize again, the issue I brought up is about changing variables through the WorkSpace, and the listener function partialy reacting (not activating display function). It is described at the main thread.
Thank you for the reply,
Yuval Blutman.

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Answers (1)

Nikhil
Nikhil on 19 Dec 2022
Hi Yuval,
As I have mentioned earlier , your NumChangedEvent is triggered only when the setNumEvent function is called ( which is the case when you call the function ).
When you change the value throught workspace, no event is triggered and hence no display.
Even if you try something like objName.NumEvent = 10 from command line, the display function won't work as no event is triggered.
It is triggered only if you do objName.setNumEvent(10) ( literally call the function).
The only thing I am not able to figure out is, when I change value from workspace , the value is changed only in event and not listener.
Hope this helps.

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