Is there a built-in function to validate a class property that should be a cell array?

I'm new to classes and learning about how to define properties and validate their values.

I have a class with a property A that is a cell array of doubles (possibly matrices). For example:

A =

1×2 cell array

{[0.7000]} {[0.9000]}

classdef MKFObserver < matlab.mixin.Copyable

    properties (SetAccess = immutable)
        Ts {mustBeNumeric}
        n {mustBeInteger}
        %...etc
        
    end
    properties
        A   % how to validate this?
        B
        C
        D
        P {mustBeNumeric}
        Q {mustBeNumeric}
        R {mustBeNumeric}
        %...etc
        
    end

Can I use a built in function like {mustBeNumeric} or do I need to write my own validation function?

[per isakson]

Did you check out mustBeUnderlyingType ?

[Bill Tubbs]

Thanks. That will do the first part. But I'll have to upgrade my MATLAB now! (Introduced in R2020b). I admit I have been putting it off for too long...

[per isakson]

Something like this

A  (1,2)  {mustBeUnderlyingType(A,'cell')}

Not tested

Answer 1

[Edric Ellis]

Rather than a validator, you could perhaps just use the class specification? (In my code below I'm using a function with an arguments block, but the syntax is exactly the same as a properties block in a classdef). Note that this will accept anything that can be converted to a cell, if you care about distributed arrays, then you should use the approach suggested by @Sean de Wolski.

myFcn({1,2}); % works
myFcn([1,2]); % fails

Error using solution>myFcn
Invalid argument at position 1. Value must be of type cell or be convertible to cell.

function myFcn(in)
arguments
    in (1,2) cell
end
% do stuff
end

[Bill Tubbs]

This worked! I just did this:

classdef MKFObserver < matlab.mixin.Copyable
    properties
        A cell
        B cell
    %...etc


% Test:
>> MKFObserver([0.7 0.9], ...)
Error setting property 'A' of class 'MKFObserver':
Invalid data type. Value must be cell or be convertible to cell

It doesn't check the underlying type of the elements of the cell array but I decided in the end I don't want this level of validation. Thanks.

Answer 2

[Matt J]

There is always iscell():

classdef
    ...
  methods
  function obj=set.A(obj,A)
    assert(iscell(A),'Value assigned to A must be cell array'); 
    obj.A=A;
  end
 end
end

Answer 3

[Sean de Wolski]

I think you'll have to write your own. Must be underlying type is for distributed, gpuArrays and others that masquerade as the underlying type.

mustBeUnderlyingType({pi},'double')

Value must have underlying type 'double'.

You could probably get away with this as your validator: cellfun(@(x)mustBeA(x, 'double'),PropertyName)

c = {pi,magic(3)}
d = {pi, "hello"}
cellfun(@(x)mustBeA(x, 'double'),c)
cellfun(@(x)mustBeA(x, 'double'),d)