Is there a Matlab equivalent to Pythons @classmethod?

In Matlab, I want to create an alternative constructor using a static method, and I want this constructor to be able to inherit to subclasses. I fail to do so, because I cannot get a reference to the calling class inside a static method.

Consider this example code with superclass A that has an alternative constructor fromSomething:

classdef A

    properties
        a
    end
    
    methods
        function obj = A(a)
            if nargin
                obj.a = a;
            end
        end
    end

    methods(Static)

        function obj = fromSomething()
            obj = A(42);
        end
    end
end

An instance of A can be created by calling A.fromSomething().

Now consider subclass B:

classdef B < A

    methods
        function someFunctionality(obj)
        end
    end

end

Calling B.fromSomething() gives an object of type A. That is not the desired behavior. How can this code be changed such that B.fromSomething() gives me an object of type B with minimal code re-use?

In Python, this would be done using a @classmethod decorator.

from dataclasses import dataclass

@dataclass
class A:
    a : float

    @classmethod
    def from_something(cls):
        return cls(42)
    

class B(A):

    def some_functionality(self):
        ...

Note that in the Python code B.from_something() will return an object of type B.

I've tried to obtain the class name of the current class using dbstack:

...
        function obj = fromSomething()
            cls = currentClass();
            obj = feval(cls.Name, 42);
        end
...

function    [ cls, str ] = currentClass( )
% Taken from https://nl.mathworks.com/matlabcentral/answers/77387-any-way-to-get-the-current-class
dbk = dbstack( 1, '-completenames' );
if isempty( dbk )
    str = 'base';
else
    str = dbk(1).name;
end
cac = regexp( str, '\.', 'split' );
switch  numel( cac )
    case 1
    case 2
        cls = meta.class.fromName( cac{1} );
        str = cac{2};
    case 3
    otherwise
end
end

However, dbstack returns the class that the function is defined on (in this case: A), rather than the class the function is called on (in this case, B when calling B.fromSomething()). As a result B.fromSomething() will still return an object of type A.

I would say that reading from the docs, MATLAB does not seem to have class methods:

https://uk.mathworks.com/help/matlab/matlab_oop/how-to-use-methods.html

In fact this is not a common type of method in most programming languages.

@staticmethod is a very Pythony thing, and you need it because Python doesn't do function overloading, and doesn't make it easy to simulate it. In MATLAB it is quite common for a function to have multiple signatures, and do different things depending on which inputs are given.

Your use case, I presume, is to construct an object given a specific input something: A.fromSomething(something), as opposed to a plain A(), or a A.fromFoo(foo).

In MATLAB all these cases are typically handled by the same constructor. You can make it look like this:

classdef A
   % ...
   methods
      function obj = A(arg)
         if nargin == 0
            % case A()
         else
            if isa(arg, 'Something')
               % case A(something)
            elseif isa(arg, 'Foo')
               % case A(foo)
            else
               error('Illegal input')
            end
         end
      end
   end
end