The QSet::const_iterator 类提供 STL 样式 const 迭代器为 QSet . 更多...
| 头： | #include <const_iterator> |
| qmake: | QT += core |
| Since: | Qt 4.2 |
| typedef | difference_type |
| typedef | iterator_category |
| typedef | pointer |
| typedef | reference |
| typedef | value_type |
| const_iterator () | |
| const_iterator (typename Hash::const_iterator i ) | |
| 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 ) |
| bool | operator== (const const_iterator & other ) const |
The QSet::const_iterator 类提供 STL 样式 const 迭代器为 QSet .
QSet features both STL 样式迭代器 and Java 风格迭代器 . 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.
QSet <Key, T>::const_iterator allows you to iterate over a QSet . If you want to modify the QSet as you iterate over it, you must use QSet::iterator instead. It is generally good practice to use QSet::const_iterator on a non-const QSet as well, unless you need to change the QSet through the iterator. Const iterators are slightly faster, and can improve code readability.
默认 QSet::const_iterator constructor creates an uninitialized iterator. You must initialize it using a function like QSet::begin (), QSet::end ()，或 QSet::insert () before you can start iterating. Here's a typical loop that prints all the items stored in a set:
QSet<QString> set; set << "January" << "February" << ... << "December"; QSet<QString>::const_iterator i; for (i = set.begin(); i != set.end(); ++i) qDebug() << *i;
STL-style iterators can be used as arguments to 一般算法 . For example, here's how to find an item in the set using the qFind() algorithm:
QSet<QString> set; ... QSet<QString>::iterator it = qFind(set.begin(), set.end(), "Jeanette"); if (it != set.constEnd()) cout << "Found Jeanette" << endl;
警告： 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 隐式共享迭代器问题 .
另请参阅 QSet::iterator and QSetIterator .
Makes the iterator go back by j items. (If j is negative, the iterator goes forward.)
This operation can be slow for large j 值。
另请参阅 operator+= () 和 operator- ().
Advances the iterator by j items. (If j is negative, the iterator goes backward.)
This operation can be slow for large j 值。
另请参阅 operator-= () 和 operator+ ().
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 值。
另请参阅 operator+ ().
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 值。
另请参阅 operator- ().
这是重载函数。
The postfix -- operator (
it--
) makes the preceding item current and returns an iterator to the previously current item.
The prefix -- operator (
--it
) makes the preceding item current and returns an iterator to the new current item.
Calling this function on QSet::begin () leads to undefined results.
另请参阅 operator++ ().
这是重载函数。
The postfix ++ operator (
it++
) advances the iterator to the next item in the set and returns an iterator to the previously current item.
The prefix ++ operator (
++it
) advances the iterator to the next item in the set and returns an iterator to the new current item.
Calling this function on QSet <T>::constEnd() leads to undefined results.
另请参阅 operator-- ().
返回
true
if
other
指向与此迭代器不同的项；否则返回
false
.
另请参阅 operator== ().
返回
true
if
other
points to the same item as this iterator; otherwise returns
false
.
另请参阅 operator!= ().
Returns a pointer to the current item.
另请参阅 operator* ().
Returns a reference to the current item.
另请参阅 operator-> ().
赋值 other to this iterator.
构造副本为 other .
Synonyms for std::bidirectional_iterator_tag indicating these iterators are bidirectional iterators.
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.
另请参阅 QSet::begin () 和 QSet::end ().
这是重载函数。
构造副本为 other .
该函数在 Qt 4.2 引入。
