External class method invocation error

Error message: Error using UGV/rotateby Method 'rotateby' is not defined for class 'UGV' or is removed from MATLAB's search path

I am getting this error when calling a method defined in a sibling function m-file within the class folder holding the class definition file. Here is the directory structure, which looks correct according the the help documentation.

Strange that this code was executing without error 1 day ago. I tried clearing and recreating the object instance. I rehashed the path. I examined the path and the parent folder of the class folder @UGV is on Matlab's search path as per definitions in help for external methods.

Here is the a snippet of the class definition in @UGV/UGV.m:

classdef UGV
    
    properties
        dunit = 'foot';
        wheeltrack = 2.5;   % default track 2.5 ft
        wheelbase = 1.25;   % default wheelbase 1.25 ft
        rho;                % rotation radius
        ...
    end
    
    methods
        function obj = UGV()
            tau = obj.wheeltrack / 2;
            beta = obj.wheelbase / 2;
            obj.rho = sqrt(tau^2 + beta^2);	% rotation radius
        end
        ...
        
        % Rotation trajectory methods
        traj = rotateby(obj, ang);              % core radian version <<<<< This is the method that is failing
        function traj = rotatebyd(obj, deg)     % degree version <<<< an internal method that executes
            traj = rotateby(obj, deg/180*pi);   % but fails on call to external method
        end
    ...
    end
...
end

Here is the signature in the @UGV/rotateby.m file

function traj = rotateby(obj, ang)
% rotate UGV instance by angle ang
...
end

Again everything was working until just recently, so I am not sure what is broken. The path and directory structure looks correct. The method signature in the classdef matches that of the external method file. The problem is not an execution error, but the fact that Matlab can't seem to find the method file or doesn't associate it with the class. But help says that Matlab interprets all function m-files in the same class folder as methods of the sibling classdef.

[Steven Lord]

Strange that this code was executing without error 1 day ago.

Do you remember what changed between the last time you were able to call the rotateby method successfully and the first time you were unable to call it successfully?

Can you show us your exact call to rotateby along with the full text of the error message (including the stack information that shows which functions were called along the way?)

[John Dolan]

Okay. This morning as a last resort, I quit my Matlab session and restarted.

And magically, the issue disappeared...??

I'm not sure what was corrupted, but Mathworks may want to log the issue in case other users encounter this.

[Catalytic]

but Mathworks may want to log the issue in case other users encounter this.

It's doubtful that they will. Matt J has already pointed out an error in your set-up. Any MathWorks staff who read this have no reason to think the issue goes any deeper than that.

Answer 1

[Matt J]

@UGV is on Matlab's search path

It should not be. The parent folder of @UGV should be on the search path, but not @UGV itself.

[John Dolan]

This must have been the problem. However, when I checked 'path' the class folder didn't appear... or perhaps I missed it. I must have done an add folder and subfolders in an ancestor directory.

Anyway, good to have a handle on what caused this, and I will be more careful going forward.

Thx.