appdesigner No appropriate method, property Error

I am having a problem with the push button , shall you please help me first with this ? cause this is the vlaue I need to pass :

my code in appdesigner :

 % Button pushed function: ChooseDirectoryButton
        function ChooseDirectoryButtonPushed(app, event)
            global currentFolder
            app.ChooseDirectory.value=uigetdir;
            currentFolder= app.ChooseDirectory.value;
            cd(currentFolder)

and throught the other button I do :

% Button pushed function: StartButton
        function StartButtonPushed(app, event)
            run(filename)
        end

But when I press the StartButton , I get the Error :

No appropriate method, property, or field 'ChooseDirectory' for class 'app1'.
Error in app1/ChooseDirectoryButtonPushed (line 15)
            app.ChooseDirectory.value=uigetdir;
 
Error using matlab.ui.control.internal.controller.ComponentController/executeUserCallback (line 309)
Error while evaluating Button PrivateButtonPushedFcn.