Calling a class method from a GUI

Hello there?

I am making a OOP test program that we can run at a GUI. The code for the class is

classdef test_1 < handle

    properties 
        name
        connectStatus = 0
    end

    methods
        %   Constructor
        function obj = test_1(test_name)
            obj.name = test_name
        end

        function status =  getStatus(obj)
            status = obj.connectStatus
        end

        function obj = setStatus(obj, newStatus)
            obj.connectStatus = newStatus
        end

    end
end

When I run this on workspace, I found that it works fine. I can check the values of the attributes of the object and I can run the method suich as getStatus, setStatus.

Now I made a GUI and tried to run the method whenever I push a button on the GUI. But Matlab gives me error messages like

'Undefined variable "obj" or class "obj.getStatus"'.

Here, obj is the object that I created and getStatus is the method.

I think the problem is simple but I do not know how to solve this.

So, I will be very thankful if someone give me a tip.

Thanks.

[snow John]

Hello sir，

I have met the same problem ，can you give me some cases as reference.

Your help will be appreciated.

Bset!

-John

Answer 1

[Geoff Hayes]

Wooshik - I suspect that what is happening is that you have defined your obj object either in the base workspace (outside of the GUI) or you have created it as a local variable in one callback or the Opening Function of your GUI and are trying to reference it in the push button callback. If either is the case, then the error message makes sense since obj is not part of the function workspace (see http://www.mathworks.com/help/matlab/matlab_prog/base-and-function-workspaces.html for an explanation of the workspaces).

If you want to reference the obj across callback within your GUI, and assuming that you have used GUIDE to create the GUI, then use the handles object to store this data. For example, if you create obj in the Opening Function as

 function myGui_OpeningFcn(hObject, eventdata, handles, varargin)

 % Choose default command line output for untitled
 handles.output = hObject;

 % create the obj object
 obj = test_1('Any name');

 % save obj as a field within handles
 handles.obj = obj;

 % Update handles structure
 guidata(hObject, handles);

The order in the above is important - we create the object obj, save it as a field of handles, and then update the handles structure with guidata so that all other callback will have the updated version of handles.

Now in your push button callback you would do something like

 function pushbutton1_Callback(hObject, eventdata, handles)

 if isfield(handles,'obj')

     myObj = handles.obj;

     myObj.getStatus;
 end

In the above, we are checking to see if the obj field exists within handles before trying to access it.

Try the above and see what happens!

[Wooshik Kim]

Thank you very much Geoff,

Your analysis is quite right. I defined the object in the base workspace because my intention is that several GUI's will access the same object and its methods and this object will manage how many GUI's are connected and left.

Right now, I am not sure whether your answer will exactly solve what I am trying to do, however your answer definitely gave me an idea of what I am going to next. I think I will try making another GUI that manages the object.

Thank you very much. I really appreciate your help.