Finds the single element in this stream matching test
.
Like lastWhere, except that it is an error if more than one matching element occurs in the stream.
Future<T> singleWhere(bool test(T element), {T orElse()}) { _Future<T> future = new _Future<T>(); T result = null; bool foundResult = false; StreamSubscription subscription; subscription = this.listen( (T value) { _runUserCode(() => true == test(value), (bool isMatch) { if (isMatch) { if (foundResult) { try { throw IterableElementError.tooMany(); } catch (e, s) { _cancelAndErrorWithReplacement(subscription, future, e, s); } return; } foundResult = true; result = value; } }, _cancelAndErrorClosure(subscription, future)); }, onError: future._completeError, onDone: () { if (foundResult) { future._complete(result); return; } try { if (orElse != null) { _runUserCode(orElse, future._complete, future._completeError); return; } throw IterableElementError.noElement(); } catch (e, s) { _completeWithErrorCallback(future, e, s); } }, cancelOnError: true); return future; }
© 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/2.0.0/dart-async/Stream/singleWhere.html