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

Asked by Oluwaseun on 10 Dec 2013
Latest activity Commented on by Zangdaarr on 20 Jan 2016
Here's an example of what I am trying to do:
classdef Colors
properties
R = 0;
G = O;
B = 0;
end
methods
function c = Colors(r , g, b)
c.R = r; c.G = g; c.B = b;
end
end
enumeration
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)
end
end
>> c = Colors.Red
??? Error using ==> Colors
Attempt to define enumeration without Enumeration class attribute in class 'Colors'.

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1 Answer

Answer by Brad 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
enumeration
Red ([1, 0, 0])
Orange ([1,.5, 0])
Yellow ([1, 1, 0])
end
end
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];
end
end
Now we get our desired results:
>> MyColors.Red
ans =
1 0 0

  1 Comment

Matlab really has its own way to copy OOL which challenge all logic and common sense.

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