How to create an async callback in Flutter/Dart?

Question

I'm trying to add an async callback to a model in a flutter application so the model can give the view an opportunity to show some dialog before the model continues on. However, I can't seem to find an async callback. I see VoidedCallback but I don't see anything like Callback<Future>.

Answer 1

Flutter has an async version of the VoidCallback typedef, namely AsyncCallback. See: https://api.flutter.dev/flutter/foundation/AsyncCallback.html

Answer 2

The VoidCallback is just a signature for method callback without parameters.

typedef VoidCallback = void Function();

You can create your own:

typedef FutureCallback = void Function(Future);

Or you can just use the final Function(Function) foo = yourcallback directly.