Why does DISPLAY method in MATLAB 7.8 (R2009a) seem to call the builtin SIZE method?

I have created a custom class Foo and has overloaded the SIZE method for it:

classdef Foo

      properties

          data

      end    

      methods

          function this = Foo(x)

              this.data = x;

          end

          function res = size(this)

              res = size(this.data);        

          end

      end

end

I then create an array of Foo objects and try to find its size

v=[Foo(2) Foo(1) Foo(3)];

size(v)

The SIZE method does not work on this array, as expected and returns an error:

 ??? Error using ==> size

 Too many input arguments.

 Error in ==> Foo>Foo.size at 22

             res = size(this.data);

However, the DISP method works on this array and shows that the size of the array is 1x3. I expected the DISP method to call the size method of the class and therefore error as before.

display(v)

   1x3 Foo

   Properties:

     data

   Methods

Answer 1

[MathWorks Support Team]

The display of MATLAB objects is broken down into two categories: objects that are scalar and objects that are not. For scalar objects (as determined by mxIsScalar), display never calls SIZE. However, when you are displaying an array of Foo objects, the overloaded SIZE will be called, but in this case, it errors, is caught in the Try/Catch block, and the built-in SIZE method is used instead.