• if you want to pass function delete from class A to class B

    • don't use : final Function? delete;
    • but use : final VoidCallback? delete;

  • if you get the error null:
    use String foo? ; foo!;

  • if you want to use wait B.fun(await ...) in class A:

    • you must add Future<void/int> fun(){await ...} in class B
    • than use the await B.fun.. in class A
    • but don't forget to add async in class A..

  • if you want to use the hot reload by plugin flutter-tools

    • use the script to kill the pid of app that running