Genie connect signal

[indent=4]
uses Gtk

init
    Gtk.init (ref args)
    var test = new TestWindow ()
    test.show_all ()
    Gtk.main ()

class TestWindow : Window
    init
        title = "Test Window"
        default_height = 250
        default_width = 250
        window_position = WindowPosition.CENTER
        destroy.connect (Gtk.main_quit)
        var button = new Button.with_label ("Click me")
        button.clicked.connect (clicked_cb)
        add (button)

    def clicked_cb (btn : Button)
        title = "Hello World"
        btn.label = "Hello World"