Added a `ResultFuture` class.

lib/src/result_future.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library async.result_future;
+
+import 'dart:async';
+
+import '../result.dart';
+import 'delegate/future.dart';
+
+/// A [Future] wrapper that provides synchronous access to the result of the
+/// wrapped [Future] once it's completed.
+class ResultFuture<T> extends DelegatingFuture<T> {
+  /// The wrapped [Future].
+  Future<T> _future;
+
+  /// Whether the future has fired and [result] is available.
+  bool get hasResult => result != null;

[Lasse Reichstein Nielsen, 2015/07/09 11:18:20]

I prefer isComplete - that's the direct question, where hasResult is indirect -
you have a result if you are complete.

[nweiz, 2015/07/13 20:05:52]

Done.

+
+  /// The result of the wrapped [Future], if it's completed.
+  ///
+  /// If it hasn't completed yet, this will be `null`.
+  Result<T> get result => _result;
+  Result<T> _result;
+
+  factory ResultFuture(Future<T> future) {
+    var resultFuture;
+    resultFuture = new ResultFuture._(Result.capture(future).then((result) {
+      resultFuture._result = result;
+      return result.asFuture;
+    }));
+    return resultFuture;
+  }
+
+  ResultFuture._(Future<T> future)
+      : super(future);
+}