CancelableOperation and CancelableCompleter usage example

main.dart

import 'package:async/async.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {

  test("CancelableOperation with future", () async {
    var cancellableOperation = CancelableOperation.fromFuture(
      Future.value('future result'),
      onCancel: () => {print('onCancel')},
    );

    // cancellableOperation.cancel(); // comment/uncomment this to log the different callbacks

    cancellableOperation.value.then((value) => {
          print('then: $value'),
        });
    cancellableOperation.value.whenComplete(() => {
          print('onDone'),
        });
  });

  test("CancelableOperation with stream", () async {
    var cancellableOperation = CancelableOperation.fromFuture(
      Future.value('future result'),
      onCancel: () => {print('onCancel')},
    );

    // cancellableOperation.cancel(); // comment/uncomment this to log the different callbacks

    cancellableOperation.asStream().listen(
          (value) => {
                print('value: $value'),
              },
          onDone: () => {
                print('onDone'),
              },
        );
  });

  test("CancelableCompleter is cancelled", () async {
    CancelableCompleter completer = CancelableCompleter(onCancel: () {
      print('onCancel');
    });

    // completer.operation.cancel(); // comment/uncomment this to log the different callbacks

    completer.complete(Future.value('future result'));
    print('isCanceled: ${completer.isCanceled}');
    print('isCompleted: ${completer.isCompleted}');
    completer.operation.value.then((value) => {
          print('then: $value'),
        });
    completer.operation.value.whenComplete(() => {
          print('onDone'),
        });
  });
}