How do I invoke an event within a static method in MatLab?

Question

I have a class that is meant to be static, and therefore all methods are static. Since I'm trying to keep track of where the process is during an operation, I'm trying to fire an event periodically to update the UI. My class looks something similar to the following:

classdef foo < handle

    events
       Update
    end
    methods(Static)
        function bar1()
            ...
            notify([], 'Update', EvtData(val));
        end
    end
end

The problem is that when I run the code, and get to the notify([]... line, I get the following error:

Undefined command/function 'notify'.

I'm assuming that this has something to be done with the fact that this is a static method being called as such:

foo.bar1()

How do I fire/invoke an event within a static method in MatLab?

Answer 1

Events in MATLAB OOP are associated with a handle object that is the source of the triggered event ( notify ). You cannot register an event handler without having an object that triggers the event you are interesting in listening to ( addlistener ).

Depending on how the class fits in your application, perhaps in your case you can implement the Singleton pattern :

MyClass.m

classdef MyClass < handle
    events
        Update
    end

    %# private constructor
    methods (Access = private)
        function obj = MyClass()
        end
    end

    methods (Static)
        %# restrict instantiation of class to one object
        function obj = getInstance()
            persistent inst;
            if isempty(inst)
                inst = MyClass();
            end
            obj = inst;
        end

        %# register event listener
        function registerListener(f)
            persistent lh;
            if ~isempty(lh)
                delete(lh);
            end
            lh = addlistener(MyClass.getInstance(), 'Update', f);
        end

        %# some function that will trigger the event
        function func()
            notify(MyClass.getInstance(), 'Update')
        end
    end
end

MATLAB

>> MyClass.func
>> MyClass.registerListener(@(o,e)disp('updated'))
>> MyClass.func
updated
>> MyClass.func
updated