Dart. Late initialize final variables

It is now possible to late initialize variables. For more information see Dart’s documentation. The text below is copied from Dart’s documentation:

Late final variables

You can also combine late with final:

// Using null safety:
class Coffee {
  late final String _temperature;

  void heat() { _temperature="hot"; }
  void chill() { _temperature="iced"; }

  String serve() => _temperature + ' coffee';
}

Unlike normal final fields, you do not have to initialize the field in its declaration or in the constructor initialization list. You can assign to it later at runtime. But you can only assign to it once, and that fact is checked at runtime. If you try to assign to it more than once — like calling both heat() and chill() here — the second assignment throws an exception. This is a great way to model state that gets initialized eventually and is immutable afterwards.