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// 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;
* An interface for getting items, one at a time, from an object.
* The for-in construct transparently uses `Iterator` to test for the end
* of the iteration, and to get each item (or _element_).
* 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 using
* [moveNext] to point to the first element.
* If no element is left, then [moveNext] returns false, [current]
* returns `null`, and all further calls to [moveNext] will also return false.
* A typical usage of an Iterator looks as follows:
* var it = obj.iterator;
* while (it.moveNext()) {
* use(it.current);
* }
* **See also:**
* [Iteration](
* in the [library tour](
abstract class Iterator<E> {
* Moves to the next element.
* Returns true if [current] contains the next element.
* Returns false if no elements are left.
* It is safe to invoke [moveNext] even when the iterator is already
* positioned after the last element.
* In this case [moveNext] returns false again and has no effect.
* A call to `moveNext` may throw if iteration has been broken by
* changing the underlying collection.
bool moveNext();
* Returns the current element.
* Returns `null` if the iterator has not yet been moved to the first
* element, or if the iterator has been moved past the last element of the
* [Iterable].
* The `current` getter should keep its value until the next call to
* [moveNext], even if an underlying collection changes.
* After a successful call to `moveNext`, the user doesn't need to cache
* the current value, but can keep reading it from the iterator.
E get current;