# elementAt method

Future<T> elementAt (int index)

Returns the value of the `index`th data event of this stream.

Stops listening to this stream after the `index`th data event has been received.

Internally the method cancels its subscription after these elements. This means that single-subscription (non-broadcast) streams are closed and cannot be reused after a call to this method.

If an error event occurs before the value is found, the future completes with this error.

If a done event occurs before the value is found, the future completes with a RangeError.

## Implementation

    Future<T> elementAt(int index) {
      ArgumentError.checkNotNull(index, "index");
      RangeError.checkNotNegative(index, "index");
      _Future<T> future = new _Future<T>();
      StreamSubscription subscription;
      int elementIndex = 0;
      subscription = this.listen(
          (T value) {
            if (index == elementIndex) {
              _cancelAndValue(subscription, future, value);
              return;
            }
            elementIndex += 1;
          },
          onError: future._completeError,
          onDone: () {
            future._completeError(
                new RangeError.index(index, this, "index", null, elementIndex));
          },
          cancelOnError: true);
      return future;
    }