Why classes need 'InferiorClasses' to determine which method to call when multiple classes have the same method

Question

fa wu 2023-7-29

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2002212-why-classes-need-inferiorclasses-to-determine-which-method-to-call-when-multiple-classes-have-the

评论： fa wu 2023-7-31

Document from here .I know how to use InferiorClasses.But I don't know why I need to use InferiorClasses?

For example,there is two classes,I don't use InferiorClasses! When I use classA's methods,just use " obj_classA.MyMethod". When I use classB's methods,just use " obj_classB.MyMethod".

it's very flexible！So Why classes need 'InferiorClasses' to determine which method to call when multiple classes have the same method?

classdef  classA
       properties
           a;
       end
       methods
         function obj=classA(value)
             obj.a=value;
         end
         function MyMethod (obj,obj_classB)
             disp('The MyMethod of classA Called!');
         end
       end
end

 classdef %(InferiorClasses = {?classA}) classB 
        properties
           b;
        end
         methods
         function obj=classB(value)
             obj.b=value;
         end
         function MyMethod (obj,obj_classB)
             disp('The MyMethod of classB is Called!'); 
         end
         end
  end

  obj_classA = classA(3);
  obj_classB = classB(4);

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Answer 1

Steven Lord 2023-7-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2002212-why-classes-need-inferiorclasses-to-determine-which-method-to-call-when-multiple-classes-have-the#answer_1280522

There are several different reasons. The first is that not all of our users are familiar with or comfortable using the object.method syntax. A large subset of our user base prefers function(inputs) syntax, and in that syntax there are situations where you don't want the left-most object to control which class's overload of a method to be called.

One concrete example is this: plot(ax, obj) where ax is an axes object and obj is an object whose class has a plot method. Which plot method should this call? The axes object is the left-most object, but we don't want it to have to know about every object that could be plotted in it. So many graphics classes will define axes as an InferiorClass, to ensure that plot call would call their plot method rather than the plot method of axes.

Another is that sometimes the order of the input arguments matters. If A and B are two classes that each overload the minus method, how can we use B's minus to compute A-B? B.minus(A) computes B-A which is not what I want. But if A and B have the same priority, both A.minus(B) and A-B would call A's minus. In this case B would declare A as an InferiorClass to force A-B to call B's minus.