blob: 671f0eea0050e109ee6bbe41d902da3f5a1dc5d2 [file] [log] [blame]
// 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.collection;
/// The [HasNextIterator] class wraps an [Iterator] and provides methods to
/// iterate over an object using `hasNext` and `next`.
/// An [HasNextIterator] does not implement the [Iterator] interface.
class HasNextIterator<E> {
static const int _HAS_NEXT_AND_NEXT_IN_CURRENT = 0;
static const int _NO_NEXT = 1;
static const int _NOT_MOVED_YET = 2;
Iterator<E> _iterator;
int _state = _NOT_MOVED_YET;
bool get hasNext {
if (_state == _NOT_MOVED_YET) _move();
return _state == _HAS_NEXT_AND_NEXT_IN_CURRENT;
E next() {
// Call to hasNext is necessary to make sure we are positioned at the first
// element when we start iterating.
if (!hasNext) throw StateError("No more elements");
assert(_state == _HAS_NEXT_AND_NEXT_IN_CURRENT);
E result = _iterator.current;
return result;
void _move() {
if (_iterator.moveNext()) {
} else {
_state = _NO_NEXT;