Get all allowed values of a class property

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Alexander Jöhl
Alexander Jöhl 2021-3-29
评论： Matt J 2021-3-29
I have a class that has a property restricted to certain values (mustbemember several char arrays in this case). I also have an app that contains an object of this class. The app also has a dropdown. Now, I want to populate the dropdown item list with the allowed values of that restricted property. Is it possible to programmatically get a list of all the allowed values of the class?
  2 个评论
J. Alex Lee
J. Alex Lee 2021-3-29
i don't know if this is a good way, but since it sounds like you are the one authoring the class and controlling by comparison to lists, can you just expose that list?
Alexander Jöhl
Alexander Jöhl 2021-3-29
Thanks for your comment:
The property looks like this:
prop char {mustBeMember(prop,{'a','b','c'})} = 'a'
The list is hard coded here. I don't know how to extract it from there.

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采纳的回答

Matt J
Matt J 2021-3-29
编辑：Matt J 2021-3-29
Ran in:
Below is a rather gymnastic way of extracting the list (I admit it would be nice if this were unnecessary):
classdef myclass %Example class
properties
prop {mustBeMember(prop,{'a','b','c'})} = 'a'
end
end
m=?myclass;
str = func2str( m.PropertyList.Validation.ValidatorFunctions{1} );
C=extractBetween(str,'{','}','Boundaries','inclusive');
selections=eval(C{1})
selections = 1×3 cell array
{'a'} {'b'} {'c'}
  1 个评论
Alexander Jöhl
Alexander Jöhl 2021-3-29
Thanks for your answer. A minor point I noticed: if you have multiple properties, then you have to index into the PropertyList:
str = func2str( m.PropertyList(1).Validation.ValidatorFunctions{1} );

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更多回答（1 个）

J. Alex Lee
J. Alex Lee 2021-3-29
编辑：J. Alex Lee 2021-3-29
Ah, I should more fully embrace the validator mechanism. Here is a way by defining a custom validator, so in a way less hard-coded by relying on the same mechanism.
classdef myclass %Example class
properties (Constant)
AllowedPropVals = {'a','b','c'}
end
properties
prop {myclass.propValidator(prop)} = 'a'
propstat {mustBeMember(propstat,{'a','b','c'})} = 'a'
end
methods (Static , Access = private)
function propValidator(prop)
mustBeMember(prop,myclass.AllowedPropVals)
end
end
end
Then your app can simply access the constant property myclass.AllowedPropVals
  3 个评论
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J. Alex Lee
J. Alex Lee 2021-3-29
I didn't either, until I saw your question and wondered about it, so thank you!
Matt J
Matt J 2021-3-29
Funny that you can't just do,
properties
propstat {mustBeMember(propstat,myclass.AllowedPropVals)} = 'a'
end

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