Why does tab completion not work for certain subclass methods?

I am trying to use tab completion with methods of a subclass, but it is not showing tab completion results for these methods.

I have defined a class, "ClassA" in MATLAB. This class has a method "printX" and property, "x": 

classdef ClassA
    properties
        x
    end
    
    methods
        %% Constructor
        function obj = ClassA(x)
            obj.x = x;
        end

        %% Helper Function
        function printX(obj)
            arguments
                obj ClassA
            end
            disp(obj.x)
        end
    end
end

I also defined a class "ClassB" that inherits from "ClassA":

classdef ClassB < ClassA
    methods
        function obj = ClassB(x)
            % Create the object
            obj = obj@ClassA(x);
        end
        function Print(obj)
            arguments
                obj ClassA
            end
            % Print the object property
            obj.printX();
        end
    end
end

I used argument validation blocks in the subclass method, "Print", to validate the object, "obj", as an instance of the superclass.

While methods defined in the superclass show up with tab completion, the methods defined in the subclass do not show up in the MATLAB Command Window or MATLAB Editor. However, they appear in the output list when using the "methods" function, and they work correctly when typing the method without tab completion.

After creating an instance "MyInstance" of the subclass, tab completion does not show the "Print" method when typing "MyInstance. + <TAB>".

Why does tab completion not work for certain subclass methods?

Answer 1

[MathWorks Support Team]

This is expected behavior and can be worked around by declaring a subclass object instead of a superclass object in the argument validation block as shown below.

function Print(obj)
    arguments
        obj ClassB;
    end

    % Print the object property
    obj.printX();
end

To explain, this occurs because the method belongs to the subclass while the "argument validation" block specifies an instance of the superclass. Therefore, tab completion is not aware of the method since the method does not belong to the superclass. MATLAB is dynamically-typed, so it is aware of the method during execution, which explains why it is listed in the output of the "methods" function and why the method itself works. In contrast, tab completion does not have access to that runtime information, so it cannot provide the method in the tab completion results.