How to send data through Matlab Events and Listeners?

Question

I have a code which receives information in real-time. Every time it receives this data, I want it to notify another object which has a listener to this event and send the information my first app received. All this asynchronously. Any ideas?

Answer 1

Suppose I have a class 'myClass' that I want to listen to. First, I need to write my class with an event:

classdef myClass < handle
    properties
        % list of properties
    end 

    events
        myEvent
    end

    methods
        % ... we'll write this in a second!
    end
end

Then, we build another class to contain data we would like to pass through. This class must inherit from event.EventData:

classdef myEventData < event.EventData
    properties
        A
        B
        C
    end
    methods
        function obj = myEventData(A, B, C)
            obj.A = A;
            obj.B = B;
            obj.C = C;
        end
    end
 end

Then, in a method where you want to pass your data, construct a myEventData object and use notify to raise the event:

 methods
     function getDataAndNotify(obj)
         [A, B, C] = result_of_processing; 
         eventdata = myEventData(A, B, C);
         notify(obj, 'myEvent', eventdata);
     end
 end

OK, now your class is set up to broadcast events. How do we listen to it?

Use addlistener to set up the listener:

M = myClass;

myListener = addListener(M, 'myEvent', {@myListenerCallback});

Your callback must have at least two arguments. The first argument is the source of the event; the second is any data the event may have passed.

function myListenerCallback(obj, eventdata)
    % ...
end

In this case, obj will be the myClass obj that raised the event, and eventdata will be your myEventData object that contains the data you passed. Access the data like you would properties of any other object, i.e., eventdata.A, eventdata.B, eventdata.C.