nargout with class method handles

Assume you have the following class

classdef MyClass
    methods
        function fcn(~)
        end
    end
end

The following call of nargout

   c=MyClass;
   nargout(@c.fcn)

always returns -1, no matter how many output arguments the function has. Why is that?

I'm aware this already has been discussed here, but the proposed workaround

   nargout('MyClass>MyClass.fcn')

is not suitable if you only know the function handle. The provided answer is already 5 years old, is there an update on this shortcoming?

Answer 1

[Guillaume]

With no guarantee that it works in all cases, this may be a workaround (not a pretty one):

function nout = nargout_for_class_fhandle(fhandle)
  finfo = functions(fhandle);
  fwspace = finfo.workspace{1};
  wspacefields = fieldnames(fwspace);
  mc = metaclass(fwspace.(wspacefields{1}));
  searchnames = cellfun(@(name) sprintf('%s//.%s', wspacefields{1}, name), {mc.MethodList.Name}, 'UniformOutput', false);
  midx = find(regexp(finfo.function, searchnames, 'once'));
  mm = mc.MethodList(midx);
  nout = numel(mm.OutputNames);
end

I've not put any error checking in there and because it attempts to find the method name in the body of the anonymous function code it could be defeated.