Get all allowed values of a class property

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?

[J. Alex Lee]

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]

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.

Answer 1

[Matt J]

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'}

[Alexander Jöhl]

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} );

Answer 2

[J. Alex Lee]

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

[Alexander Jöhl]

Ah, this is elegant. I didn't know you could make custom validators. Learned something new, thank you.

[J. Alex Lee]

I didn't either, until I saw your question and wondered about it, so thank you!

[Matt J]

Funny that you can't just do,

	properties
	
		propstat {mustBeMember(propstat,myclass.AllowedPropVals)} = 'a'
		
	end