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How can I get rid of this enumeration error while using classes?

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Here's an example of what I am trying to do:
classdef Colors
R = 0;
G = O;
B = 0;
function c = Colors(r , g, b)
c.R = r; c.G = g; c.B = b;
Red (1, 0, 0)
Orange (1,.5, 0)
Yellow (1, 1, 0)
Green (0, 1, 0)
Blue (0, 0, 1)
Indigo (.2,0,.8)
Violet (1, 0, 1)
>> c = Colors.Red
??? Error using ==> Colors
Attempt to define enumeration without Enumeration class attribute in class 'Colors'.
  1 Comment
Captain Karnage
Captain Karnage on 7 Aug 2023
Perhaps it's because it's an old question and something you did was not supported in R2013. But in R2022b your code now works, with one exception: You have G = O (the letter O) when it should be G = 0 (zero).

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Answers (1)

Bradley Stiritz
Bradley Stiritz on 4 Jul 2014
MATLAB enumeration definitions can't be nested within another classdef definition, as your code attempts to do. That would be very convenient & useful, but unfortunately isn't supported currently.
You need to define your enumeration as its own class in its own @-folder. Also, note that since you've supplied your own enumeration values, your class needs to inherit support for those values. However, your numeric vector values aren't specified properly; they need to be within brackets. Here's how your classdef would need to look.. (I'm only showing the first few rows)
classdef MyColors < double
Red ([1, 0, 0])
Orange ([1,.5, 0])
Yellow ([1, 1, 0])
Unfortunately, when we try to use this, we find that vector values aren't allowed :(
>> MyColors.Red
In class 'MyColors', enumeration member named 'Red' must be scalar.
So you'll have to find a different way to implement your idea. I would suggest considering an ordinary classdef with constant properties, a la :
classdef MyColors
properties (Constant)
Red = [1, 0, 0];
Orange = [1,.5, 0];
Yellow = [1, 1, 0];
Now we get our desired results:
>> MyColors.Red
ans =
1 0 0
  1 Comment
Zangdaarr on 20 Jan 2016
Matlab really has its own way to copy OOL which challenge all logic and common sense.

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