calling subclass method does not pass the obj only the argument

Question

Micke Malmström 2017-12-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/372773-calling-subclass-method-does-not-pass-the-obj-only-the-argument

回答： Micke Malmström 2018-4-25

I have these classes

 classdef LUS < handle
  methods 
   function fun1(obj,extravalues)
    %some code using extravalues
   end
  end
 end

and:

 classdef FLUS < LUS
  methods
   function fun1(obj,extravalues)
     fun1@LUS(obj, extravalues);
       %some extra code using extravalues
   end
  end
 end

however when I run

 OBJ=FLUS;
 OBJ.fun1(extravalues);

then as "fun1" of "LUS" is executed nargin is only 1. Meaning that obj="extravalues" and extravalues is undefined...

How should I call fun1@LUS(obj, extravalues) so that "obj" is passed as "obj" and "extravalues" is passed as "extravalues"?

4 个评论
显示 2更早的评论隐藏 2更早的评论

Steven Lord 2017-12-13

在 MATLAB Online 中打开

That's not the behavior I see in release R2017b. Here are my versions of your class definitions, with a few lines added to display some diagnostic information.

>> type LUS.m
   classdef LUS < handle
    methods 
     function fun1(obj,extravalues)
      %some code using extravalues
      disp('Inside fun1 in LUS')
      whos
      nargin
     end
    end
   end
>> type FLUS.m
   classdef FLUS < LUS
    methods
     function fun1(obj,extravalues)
         disp('Inside fun1 in FLUS')
         whos
         nargin
       fun1@LUS(obj, extravalues);
         %some extra code using extravalues
     end
    end
   end

Here's how I used those classes.

>> OBJ=FLUS;
>> extravalues = 1:10;
>> OBJ.fun1(extravalues);
Inside fun1 in FLUS
  Name             Size            Bytes  Class     Attributes
    extravalues      1x10               80  double              
    obj              1x1                 8  FLUS                
ans =
       2
Inside fun1 in LUS
  Name             Size            Bytes  Class     Attributes
    extravalues      1x10               80  double              
    obj              1x1                 8  FLUS                
ans =
       2

As you can see, the superclass method received both the inputs with which the subclass method called it. You didn't mention what you used for extravalues, so I chose a simple double array.

Adam 2017-12-13

编辑：Adam 2017-12-13

在 MATLAB Online 中打开

Personally, when doing this I favour the option of not over-riding the base class function and instead having a setup as:

classdef LUS < handle
   methods 
      function fun1(obj,extravalues)
         % Do some common base class stuff
         doFun1( obj, extravalues )
      end
   end
    methods( Access = protected )
       function doFun1( obj, extravalues )
       end
    end
end

and in the subclass:

classdef FLUS < LUS
   methods( Access = protected )
     function doFun1(obj,extravalues)
         %some extra code using extravalues
     end
   end
end

There are also variations on that that I use, depending if the subclass should always add something (in which case make the function abstract in the super class) or if it should be pre- or post- what the base class does.

It is mostly just a question of taste though. Your version should work from what I see.

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