How to check if an object is from a certain class object?

I want to check if an item is actually a box, so here is a box:

    classdef Box

    properties
        u
        v
        n
    end

    methods
        %%constructor
        function obj = Box(u,v)
            if nargin == 0
                error('insert parameters u and v');
            end

            if nargin == 2 && isvector(u) && isvector(v)
                if length(u) ~= length(v)
                    error('length of u unequals length of v')
                end
                for i = 1:length(u)
                    if u(i) == v(i)
                        error('%s th component of input are the same', i)
                    end
                end
                obj.u = u;
                obj.v = v;
                obj.n = length(u);
                return;
            end
        end
    end
end

and then I used

u = zeros(3,1); v = ones(3,1); a = Box(u,v)
isa(a,Box)

but isa(object,Classobject) is somehow function calling constructor of the class object, and returns the error from which nargin == 0. How do I properly check if object a is a box?

[per isakson]

>> isa( a, 'Box' )
ans =
     1

[Al in St. Louis]

This bites me each time I go to use it! (I only use it once every two to three years.)

Answer 1

[Sayyed Ahmad]

try this:

isequal(class(a),'Box')
ans =
    1

[Steven Lord]

That would work in this particular example, but it wouldn't work with subclasses. Let's take two classes:

classdef Animal
    % Some general methods and properties: Move, numberOfLegs, etc.
end

and

classdef Dog < Animal
    % Some specific methods and properties: Bark, breed (property), etc.
    % This also inherits Move and numberOfLegs from Animal
end

If we create a Dog object, is it an Animal?

D = Dog();
isa(D, 'Animal') % true
isequal(class(D), 'Animal') % false