Override how the value of a user defined class is displayed when it is a field of a structure

Question

Clark Williams 2012-10-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/50549-override-how-the-value-of-a-user-defined-class-is-displayed-when-it-is-a-field-of-a-structure

I have created my own class to act like an enumerated type. I haver overridden the method disp() so when a variable containing that type is displayed in the Command Window it shows something meaningful (specifically, the name of that enumerated value.)

classdef MyEnumeratedType

    properties(Constant)
        ENUMVAL1     = MyEnumeratedType(1, 'ENUMVAl1');
        ENUMVAL2     = MyEnumeratedType(2, 'ENUMVAL2');
        ENUMVAL3     = MyEnumeratedType(3, 'ENUMVAL3');
    end
    properties(Access=private)
        ordinal
        name
    end
    methods(Access=private)
        function this = MyEnumeratedType(ord, name)
            this.ordinal = ord;
            this.name = name;
        end
    end
    methods
        function disp( this )
            disp(this.name);
        end
    end

end

So when I assign it to a variable in the command window, I get the desired output:

>> x = MyEnumeratedType.ENUMVAL2

x =

ENUMVAL2

So far so good. BUT when I assign a value of type MyEnumeratedType to the field of a structure, the display of that structure doesn't display the value, but only tells me that I have a value of type MyEnumeratedType.

>> mystruct.field1 = 42

mystruct =

field1: 42

>> mystruct.field2 = MyEnumeratedType.ENUMVAL3

mystruct =

    field1: 42
    field2: [1x1 MyEnumeratedType]

How do I get the value of field2 to show up like it does for the double value in field1?

Question also posted at StackOverflow at http://stackoverflow.com/questions/12846290/override-how-the-value-of-a-user-defined-class-is-displayed-when-it-is-a-field-o

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Matt J 2012-10-11

编辑：Matt J 2012-10-11

Any reason you're not using MATLAB's enumeration classes?

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Answer 1

Daniel Shub 2012-10-11

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/50549-override-how-the-value-of-a-user-defined-class-is-displayed-when-it-is-a-field-of-a-structure#answer_61705

I think you would need to overload disp for the struct class.

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Clark Williams 2012-10-11

How would one accomplish that? For primitive types, disp() is a built-in.

Matt J 2012-10-11

You can create your own directory @struct and put a revised definition of the display() method in there. You can also call the builtin version of struct/display using the BUILTIN function to help you overload it. Seems like a lot of work to me, however.

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