The QSet::const_iterator 类提供 STL 样式 const 迭代器为 QSet . 更多...
iterator_category |
const_iterator () | |
const_iterator (const QSet<T>::iterator & other ) | |
const_iterator (const QSet<T>::const_iterator & other ) | |
bool | operator!= (const QSet<T>::const_iterator & other ) const |
const T & | operator* () const |
QSet<T>::const_iterator & | operator++ () |
QSet<T>::const_iterator | operator++ (int) |
const T * | operator-> () const |
QSet<T>::const_iterator & | operator= (const QSet<T>::const_iterator & other ) |
bool | operator== (const QSet<T>::const_iterator & other ) const |
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 = {"January", "February", ... "December"}; // i is QSet<QString>::const_iterator for (auto i = set.cbegin(), end = set.cend(); i != 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; ... const auto predicate = [](const QString &s) { return s.compare("Jeanette", Qt::CaseInsensitive) == 0; }; QSet<QString>::const_iterator it = std::find_if(set.cbegin(), set.cend(), predicate); 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 .
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 ().
构造副本为 other .
赋值 other to this iterator.
Returns a reference to the current item.
另请参阅 operator-> ().
Returns a pointer to the current item.
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!= ().
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== ().
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.
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.
这是重载函数。
构造副本为 other .