How to wait for "notify" to call and execute all listeners in Matlab 2015b?

I have two classes: A and B. A notifies data change using "notify". Class B has listeners which handle A.notify.

I want to make sure that all listeners added to all instances of class B are called and executed before I call any other function of B.

Answer 1

[BhaTTa]

To ensure that all listeners in class B are executed before any other function of B is called, you can use a few strategies to manage the flow of your program. Here’s a structured approach:

tep-by-Step Solution

1. Set Up Class A: Class A should have an event that it notifies whenever data changes.
2. Set Up Class B: Class B should have listeners that respond to the event from class A. You will need to ensure that these listeners are executed before other methods in class B.
3. Use a Flag or State Variable: In class B, use a flag or state variable to track whether the listeners have been executed. This can help control when other methods are allowed to run.

Example Implementation:

Class A

classdef A < handle
    events
        DataChanged
    end
    
    methods
        function notifyChange(obj)
            notify(obj, 'DataChanged');
        end
    end
end

Class B

classdef B < handle
    properties (Access = private)
        listeners
        listenersExecuted = false
    end
    
    methods
        function obj = B(source)
            % Add a listener to the DataChanged event of class A
            obj.listeners = addlistener(source, 'DataChanged', @(src, event)obj.handleDataChange(src, event));
        end
        
        function handleDataChange(obj, ~, ~)
            % Perform actions when data changes
            disp('Data changed!');
            % Set the flag to true after handling
            obj.listenersExecuted = true;
        end
        
        function someMethod(obj)
            % Check if listeners have been executed before proceeding
            if ~obj.listenersExecuted
                error('Listeners have not been executed yet.');
            end
            % Proceed with the method's operations
            disp('Executing someMethod...');
        end
    end
end

Usage Example

% Create an instance of class A
a = A();

% Create an instance of class B with a as the source
b = B(a);

% Notify change in class A
a.notifyChange();

% Call someMethod in class B (this will only succeed if listeners have executed)
b.someMethod();