using Gtk;
/* When button click signal received */
public void on_button1_clicked (Button source) {
    /* change button label to clicked! */
    source.label = "Clicked!";
    stderr.printf ("Clicked! --> ");
}

public void on_window1_destroy (Window source) {
    /* When window close signal received */
    Gtk.main_quit ();
}

int main (string[] args) {
    Gtk.init (ref args);

    var builder = new Builder ();
    /* Getting the glade file */
    builder.add_from_file ("sample.ui");
    builder.connect_signals (null);
    var window = builder.get_object ("window1") as Window;
    var entry = builder.get_object ("entry1") as Entry;
    var button = builder.get_object ("button1") as Button;
    /* thats another way to do something when signal received */
    button.clicked.connect (() => {
        stderr.printf ("%s\n", entry.get_text ());
    });
    window.show_all ();
    Gtk.main ();

    return 0;
}