Superclass method calls subclass method: bug or feature? How to call same level method?

Hi,

I have two classes, B inherited from A, with an overloaded function Init(), defined as follows:

A.m:

classdef A
  methods
    function obj = A()
      disp('A.Constructor()');
      obj = obj.Init();
    end
    
    function obj = Init(obj)
      disp('A.Init()');
    end
  end
end

B.m:

    classdef B < A
      methods
        function obj = B()
          disp('B.Constructor()');
          obj = obj.Init();
        end
        
        function obj = Init(obj)
          disp('B.Init()');
        end
      end
    end

If I instantiate B, the display is as follows:

A.Constructor()
B.Init()
B.Constructor()
B.Init()

Which means, that the superclass constructor called the subclass' Init() function. Is this a bug or a feature? If I want the superclass call it's own Init() function, what can I do? I cannot write Init@A, it returns an error, that A is not a superclass of A, which is true.

Thanks, Istvan

Answer 1

[Image Analyst]

Why can't it be both?

Answer 2

[Informaton]

I think this is normal behavior, as sometimes you want to call the superclass init method (like here), but in other case you may not want to.

To get the behavior you want in this example, change your B.m file to the following:

classdef B < A
  methods
    function obj = B()
      disp('B.Constructor()');
    end
      
    function obj = Init(obj)
      Init@A(obj);
      disp('B.Init()');
    end
  end
end

Instantiating B now produces the following:

A.Constructor()
A.Init()
B.Init()
B.Constructor()

You do not need to call obj.Init() in B's constructor, since you already call it obj.Init() in its superclass constructor (i.e. in A.m), which is invoked automatically prior to the subclass constructor finishing as shown in your example instantiation.

Here is a link that describes how to do this: https://www.mathworks.com/help/matlab/matlab_oop/calling-superclass-methods-on-subclass-objects.html