Errors in listener callbacks

I have an app built in MATLAB App Designer. the underlying code utlizes events and listeners. my problem is this: Whenever an error occurs in the code, the app needs to know about this. when the error occurs in the code itself, there are built in "catch" commands that notify the GUI.

However, when an error occurs in one of the listener callbacks, there is some built in mechanism that replaces the error with a warning. Instead of getting an error message we get a warning: "error occurred during execution of listener callback" and a description of the error message.

Is there a way to cancel this mechanism? to let the errors in listener callbacks become actual error messages? or maybe a way to notify the app in case of a warning? something like try catch that includes warnings?

many thanks

Nathan

Answer 1

[Adam Danz]

> Is there a way to cancel this mechanism? to let the errors in listener callbacks become actual error messages?

No, there isn't an off-switch to this behavior.

> or maybe a way to notify the app in case of a warning?

It's unclear what listeners you are refering to but I'll assume they were added by the developer of the app rather than by app-designer. One idea is to wrap the listener's callback function within a try/catch and to take some action within the catch block when there is an error. However, warnings are not caught by the try-block.

Another idea is to use lastwarn to clear the last-warning-history at the beginning of the listener's callback and then to query lastwarn again at the end of the callback to determine if a warning was thrown.

Neither of these potential solutions would catch warnings that are thrown prior to or after reaching the callback function.

lastwarn('')  % clear last warning
% < function code goes here >
[msg, id] = lastwarn(); 
if ~isempty(msg)
    % take action on warning
end