const_iterator Class
(QLinkedList::const_iterator)The QLinkedList::const_iterator class provides an STL-style const iterator for QLinkedList. 更多...
| 头文件: | #include <const_iterator> |
| qmake: | QT += core |
公有函数
| const_iterator() | |
| const_iterator(iterator other) | |
| const_iterator(const const_iterator &other) | |
| const_iterator(const_iterator &&other) | |
| bool | operator!=(const const_iterator &other) const |
| const T & | operator*() const |
| const_iterator | operator+(int j) const |
| const_iterator & | operator++() |
| const_iterator | operator++(int) |
| const_iterator & | operator+=(int j) |
| const_iterator | operator-(int j) const |
| const_iterator & | operator--() |
| const_iterator | operator--(int) |
| const_iterator & | operator-=(int j) |
| const T * | operator->() const |
| const_iterator & | operator=(const const_iterator &other) |
| const_iterator & | operator=(const_iterator &&other) |
| bool | operator==(const const_iterator &other) const |
详细描述
The QLinkedList::const_iterator class provides an STL-style const iterator for QLinkedList.
QLinkedList features both STL-style iterators and Java-style iterators. The STL-style iterators are more low-level and more cumbersome to use; on the other hand, they are slightly faster and, for developers who already know STL, have the advantage of familiarity.
QLinkedList<T>::const_iterator allows you to iterate over a QLinkedList<T>. If you want modify the QLinkedList as you iterate over it, you must use QLinkedList::iterator instead. It is generally good practice to use QLinkedList::const_iterator on a non-const QLinkedList as well, unless you need to change the QLinkedList through the iterator. Const iterators are slightly faster, and can improve code readability.
The default QLinkedList::const_iterator constructor creates an uninitialized iterator. You must initialize it using a function like QLinkedList::constBegin(), QLinkedList::constEnd(), or QLinkedList::insert() before you can start iterating. Here's a typical loop that prints all the items stored in a list:
QLinkedList<QString> list; list.append("January"); list.append("February"); ... list.append("December"); QLinkedList<QString>::const_iterator i; for (i = list.constBegin(); i != list.constEnd(); ++i) cout << *i << endl;
STL-style iterators can be used as arguments to generic algorithms. For example, here's how to find an item in the list using the qFind() algorithm:
QLinkedList<QString> list; ... QLinkedList<QString>::iterator it = qFind(list.constBegin(), list.constEnd(), "Joel"); if (it != list.constEnd()) cout << "Found Joel" << endl;
Multiple iterators can be used on the same list. If you add items to the list, existing iterators will remain valid. If you remove items from the list, iterators that point to the removed items will become dangling iterators.
Warning: Iterators on implicitly shared containers do not work exactly like STL-iterators. You should avoid copying a container while iterators are active on that container. For more information, read Implicit sharing iterator problem.
参见 QLinkedList::iterator and QLinkedListIterator.
成员函数
const_iterator::const_iterator()
Constructs an uninitialized iterator.
Functions like operator*() and operator++() should not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it.
参见 QLinkedList::constBegin() and QLinkedList::constEnd().
const_iterator::const_iterator(iterator other)
Constructs a copy of other.
const_iterator::const_iterator(const const_iterator &other)
Constructs a copy of other.
const_iterator::const_iterator(const_iterator &&other)
Move-copy constructor.
bool const_iterator::operator!=(const const_iterator &other) const
Returns true if other points to a different item than this iterator; otherwise returns false.
参见 operator==().
const T &const_iterator::operator*() const
Returns a reference to the current item.
参见 operator->().
const_iterator const_iterator::operator+(int j) const
Returns an iterator to the item at j positions forward from this iterator. (If j is negative, the iterator goes backward.)
This operation can be slow for large j values.
参见 operator-().
const_iterator &const_iterator::operator++()
The prefix ++ operator (++it) advances the iterator to the next item in the list and returns an iterator to the new current item.
Calling this function on QLinkedList::constEnd() leads to undefined results.
参见 operator--().
const_iterator const_iterator::operator++(int)
This is an overloaded function.
The postfix ++ operator (it++) advances the iterator to the next item in the list and returns an iterator to the previously current item.
const_iterator &const_iterator::operator+=(int j)
Advances the iterator by j items. (If j is negative, the iterator goes backward.)
This operation can be slow for large j values.
参见 operator-=() and operator+().
const_iterator const_iterator::operator-(int j) const
This function returns an iterator to the item at j positions backward from this iterator. (If j is negative, the iterator goes forward.)
This operation can be slow for large j values.
参见 operator+().
const_iterator &const_iterator::operator--()
The prefix -- operator (--it) makes the preceding item current and returns an iterator to the new current item.
Calling this function on QLinkedList::begin() leads to undefined results.
参见 operator++().
const_iterator const_iterator::operator--(int)
This is an overloaded function.
The postfix -- operator (it--) makes the preceding item current and returns an iterator to the previously current item.
const_iterator &const_iterator::operator-=(int j)
Makes the iterator go back by j items. (If j is negative, the iterator goes forward.)
This operation can be slow for large j values.
参见 operator+=() and operator-().
const T *const_iterator::operator->() const
Returns a pointer to the current item.
参见 operator*().
const_iterator &const_iterator::operator=(const const_iterator &other)
Assigns other to this iterator.
const_iterator &const_iterator::operator=(const_iterator &&other)
Move-assignment operator.
bool const_iterator::operator==(const const_iterator &other) const
Returns true if other points to the same item as this iterator; otherwise returns false.
参见 operator!=().