How do I validate an input method input by a object property?

I am having a class "MY_CLASS" and want to write a method. In this method I first want to validate my inputs. The input is an array which should have the same size as given by one of my object properties. How can I implement this by using the arguments block?

classdef MY_CLASS
    properties(Access=public)
        Filenames cell {mustBeA(Filenames,"cell")} = {['Testrun_xxxx']}
        Num_Files (1,1) uint32 {mustBeA(Num_Files,"uint32"), mustBePositive}  = uint32(1)
    end
    
    methods
        % Constructor
        function obj = MY_CLASS( filenames, num_Files )
            obj.Filenames = filenames; 
            obj.Num_Files = num_Files; 
        end
        
        % function where I want to do my arguments validation
        function obj = doSomething( obj, var1 )
            arguments
                obj
                var1 (:,1) double {mustBeNumeric, mustBeSpecifiedSize( obj.Num_Files, var1 )}
            end
              .
              .
              .
            
        end
    end
end



% Validation Function
function mustBeSpecifiedSize( num_elements, array )
    if not(num_elements == numel(array))
        eidType = 'mustBeSpecifiedSize:invalidNumberOfElements';
        msgType = 'Inconsistency issues at the number of elements.';
        throwAsCaller(MException(eidType,msgType)) 
    end
end

[Matt J]

Why not as you've written it now?

[AAA]

It gives me a syntax error for the obj.Num_Files function input: "Validators can only use previously declared positional arguments, the argument being validated, or literals."

Answer 1

[Matt J]

classdef myclass


    properties(Access=public)
        Filenames cell {mustBeA(Filenames,"cell")} = {['Testrun_xxxx']}
        Num_Files (1,1) uint32 {mustBeA(Num_Files,"uint32"), mustBePositive}  = uint32(1)
    end
    
    methods
        % Constructor
        function obj = MY_CLASS( filenames, num_Files )
            obj.Filenames = filenames; 
            obj.Num_Files = num_Files; 
        end
        
        % function where I want to do my arguments validation
        function obj = doSomething( obj, var1 )
            arguments
                obj
                var1 (:,1) double {mustBeNumeric, mustBeSpecifiedSize( obj, var1 )}
            end
     
        end
    end


end

% Validation Function
function mustBeSpecifiedSize( obj, array )

    num_elements=obj.Num_Files; 

    if not(num_elements == numel(array))
        eidType = 'mustBeSpecifiedSize:invalidNumberOfElements';
        msgType = 'Inconsistency issues at the number of elements.';
        throwAsCaller(MException(eidType,msgType)) 
    end
end