How do I use a class property validation function with a dynamic argument?

In Matlab OOP, I wanna use a function like mustBeEqualSize(a,b) from the Examples on function property validation to validate a property:

classdef foo
    properties
        a
        b {mustBeEqualSize(a,b)}
    end
end

However, this gives me an error.

Answer 1

[Jan Siegmund]

The problem is, that MATLAB classes only support constant arguments on property validation.

However function arguments can be validated perfectly fine with dynamic arguments.

So a workaround is to validate the arguments of the constructor:

classdef Foo
    properties
        a
        b
    end
    
    methods
        
        function obj = Foo(a,b)
            arguments
                a
                b {mustBeEqualSize(a,b)}
            end
            obj.a = a;
            obj.b = b;
        end

    end
end

[Ivan Demec]

This doesn't seem to be true with the mustBeMember function.

When I try to validate an input argument against a constant property of my class I get the following error

Example code:

classdef ContinuousSweep < handle

Class name and filename must match.

    properties (Constant)
        possibleResults = {'RMS Level','Gain','Phase','THD Ratio','THD Level','THD+N Ratio','THD+N Level','Impulse Response'}
    end

    methods
        function obj = addPrimaryResult(obj,result)
            %addPrimaryResult Adds a result of the specified type if it is allowed for this measurement type.
            arguments (Input)
                obj 
                result string {mustBeMember(result,obj.possibleResults)} % HERE it complains
            end
            disp(result)
        end %addPrimaryResult          
    end
end

I want to reuse this string array as an argument validation parameter in multiple methods and "hard coding" it seems as a bad practice. Is there any solution to this?

[Benjamin Penazek]

Commenting because I have the exact same problem (granted, I'm attempting to do it with a dependent property rather than a constant property, but still).

I hope there's a working solution soon.

[Benjamin Penazek]

One thing that does half the job is overloading the ismember function for your class. Something like the following. I say half the job, because it "works" in the way you want, but it does not offer autocomplete (no popup with 'RMS Level', 'Gain', etc. will appear when you try to call obj.addPrimaryResult()).

methods
    function boolOut = ismember(val, obj)
        boolOut = ismember(val, obj.possibleResults);
    end
end
    

[Steven Lord]

Try this:

classdef ContinuousSweep < handle
    properties (Constant)
        possibleResults = {'RMS Level','Gain','Phase','THD Ratio','THD Level','THD+N Ratio','THD+N Level','Impulse Response'}
    end

    methods
        function obj = addPrimaryResult(obj,result)
            %addPrimaryResult Adds a result of the specified type if it is allowed for this measurement type.
            arguments (Input)
                obj 
                result string {mustBePossibleResult(result)}
            end
            disp(result)
        end %addPrimaryResult          
    end
end

function mustBePossibleResult(result)
PR = ContinuousSweep.possibleResults;
assert(ismember(result, PR), ...
    result + " must be one of: " + newline + strjoin(PR, ", "))
end

You can reuse mustBePossibleResult in multiple methods, as a locally defined validation function. If the property is not Constant (and so you need to retrieve the value from the instance rather than from the class) you may need to include obj in the argument list of mustBePossibleResult but since that's a previous input argument that's okay. Then you could get obj.possibleResults inside mustBePossibleResult.