Listen for a change in a subclass property

I have a main class that includes a subclass. I would like to listen for the change in one of the properties of the subclass from within the main class. I can easily code the listner whithin the subclass however I can't find a way to notify the main class. From the main class when I try to listner for changes in the subclass as a whole nothing seems to happen. I am not sure if events would help me.

[Walter Roberson]

Is this the same question as http://uk.mathworks.com/matlabcentral/answers/225101-lisning-for-a-subclass-property ?

[Guillaume]

It looks like it to me.

Walid, if an answer doesn't work for you, then a) don't accept it and b) say so.

edit: and also, don't call your second class subclass, as it's not a subclass and you're just going to confuse everybody who try to help you. subclass has a very specific meaning in OOP.

Answer 1

[Mukul Rao]

Hi , I am not sure I completely understand the context of the question but I was able to create an example that demonstrates how to,

1. Listen to change in properties of a subclass that are inherited from the superclass.

2. Listen to change in properties of a subclass that are NOT inherited from the superclass.

In both cases, the listeners are defined in the superclass and not the subclass. To test the example, copy the two classes to separate files on your MATLAB path and use the following commands on the prompt:

    object  = sub_mainclass(1,2)
    object.prop1 = 5;
    object.prop2 = 7;

Here is the example:

classdef mainclass < handle
    %MAINCLASS Summary of this class goes here
    %   Detailed explanation goes here

      properties (SetObservable)
          prop1  
      end

      methods
          function obj = mainclass(inarg)
             obj.prop1 = inarg;
             addlistener(obj,'prop1','PostSet',@mainclass.detectcallback);  
          end

          %The function addlistenertosubclass is required unless you intend to use 
          %mainclass only with sub_mainclass

          function addlistenertosubclass(obj,propname)
             addlistener(obj,propname,'PostSet',@mainclass.detectcallback2); 
          end

          %Listeners added here
          function detectcallback(srv,even)
              disp('Detected change in inherited property')
          end

          function detectcallback2(srv,even)
              disp('Detected change in non inherited property')
          end

      end

end

and the subclass,

classdef sub_mainclass < mainclass
    %SUB_MAINCLASS Summary of this class goes here
    %   Detailed explanation goes here

      properties  (SetObservable)
          prop2
      end

      methods
          function obj = sub_mainclass(prop1,prop2)
              %Instantiate from the main class
              obj@mainclass(prop1);
              %Set property 2
              obj.prop2 = prop2;
              %Activate the listener in the main class now it is aware of
              %prop2
              addlistenertosubclass(obj,'prop2');
          end

      end

end