How to require a custom class type with addRequired?

I have a custom class,

classdef foo
    properties
        %Property stuff
        prop1;
    end
    methods
        function obj = foo( )
            %Constructor stuff.
            obj.prop1 = 'test';
        end
    end
end

and I want the input of a function to require that the variable type is this custom class.

function out = fun( varargin )
    p = inputParser;
    addRequired( p, 'InputName', @(x) isa( x, 'foo' ) );
    parse( p, varargin{:} );
    % Function stuff
end

When I try doing this

% Script.
objInstance = foo();
out = fun( 'InputName', objInstance )

I get this error:

" The value of 'InputName' is invalid. It must satisfy the function: @(x)isa(x,'foo'). "

Answer 1

[Steven Lord]

You probably want to use addParameter instead of addRequired.

If you're using release R2019b or later, consider using function argument validation instead of inputParser.

But if this function requires an input of this class, should it be a separate function or should it be a method defined inside the class itself?

classdef foo
    methods
        function out = fun(x)
            % x MUST be a foo (which could mean it's a subclass of foo)
        end
    end
end

[Dominik Mattioli]

It took me a while but I finally understand why you suggested using addParameter instead. This is a great answer to a question that I now see is a little naive, thank you.

Answer 2

[Luna]

Variable out is not defined in the function bar. Also bar is already a built-in function. Use another function name instead.

[Dominik Mattioli]

I'll edit the question to have my original class and function names. I changed them to be easier to read for this question.