hObject error in execution of a checkbox

I have been trying to execute the below mentioned code and encounter the below mentioned error

function checkbox()
handles.cbh = zeros(40,1);
handles.label = 1:40; 
    for k = 1:40
        handles.cbh(k) = uicontrol('Style','checkbox','String',handles.label(k), ...
            'Value',0,'Position',[30 20*k 130 20],        ...
            'Parent', hObject, ...
            'Callback',{@checkBoxCallback,k});
    end
guidata(hObject,handles);
    function checkBoxCallback(hObject,~,checkBoxId)
        handles = guidata(handles);
        value = get(hObject,'Value');
        if value
            switch checkBoxId
                case 1
                    fprintf('handle cb 1\n');
                case 2
                    fprintf('handle cb 2\n');
                otherwise
                    fprintf('do nothing\n');
            end
        end
    end
end

the error is

Undefined function or variable 'hObject'.

Error in checkbox (line 5)
        handles.cbh(k) = uicontrol('Style','checkbox','String',handles.label(k), ...

Answer 1

[Dennis]

Your checkbox function does not know 'hObject':

function checkbox()
handles.fig=figure;
handles.cbh = zeros(40,1);
handles.label = 1:40; 
    for k = 1:40
        handles.cbh(k) = uicontrol('Style','checkbox','String',handles.label(k), ...
            'Value',0,'Position',[30 20*k 130 20],        ...
            'Parent', handles.fig, ...
            'Callback',{@checkBoxCallback,k});
    end
guidata(handles.fig,handles);

    function checkBoxCallback(hObject,~,checkBoxId)
        handles = guidata(hObject);
        value = get(hObject,'Value');
        if value
            switch checkBoxId
                case 1
                    fprintf('handle cb 1\n');
                case 2
                    fprintf('handle cb 2\n');
                otherwise
                    fprintf('do nothing\n');
            end
        end
    end
end

[Vicky S]

thank you so much. It works.