| // Copyright (c) 2012, 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. |
| |
| part of dart.core; |
| |
| /** |
| * The [Iterator] class provides methods to iterate over an object. It |
| * is transparently used by the for-in construct to test for the end |
| * of the iteration, and to get the elements. |
| * |
| * If the object iterated over is changed during the iteration, the |
| * behavior is unspecified. |
| * |
| * The [Iterator] is initially positioned before the first element. Before |
| * accessing the first element the iterator must thus be advanced ([moveNext]) |
| * to point to the first element. If there is no element left, then [moveNext] |
| * returns false. |
| * |
| * A typical usage of an [Iterator] looks as follows: |
| * |
| * var it = obj.iterator; |
| * while (it.moveNext()) { |
| * use(it.current); |
| * } |
| */ |
| abstract class Iterator<E> { |
| /** |
| * Moves to the next element. Returns true if [current] contains the next |
| * element. Returns false, if no element was left. |
| * |
| * It is safe to invoke [moveNext] even when the iterator is already |
| * positioned after the last element. In this case [moveNext] has no effect. |
| */ |
| bool moveNext(); |
| |
| /** |
| * Returns the current element. |
| * |
| * Return [:null:] if the iterator has not yet been moved to the first |
| * element, or if the iterator has been moved after the last element of the |
| * [Iterable]. |
| */ |
| E get current; |
| } |