const_iterator Class
(QSet::const_iterator)The QSet::const_iterator class provides an STL-style const iterator for QSet. More...
Header: | #include <const_iterator> |
qmake: | QT += core |
Since: | Qt 4.2 |
Public Types
typedef | difference_type |
typedef | iterator_category |
typedef | pointer |
typedef | reference |
typedef | value_type |
Public Functions
const_iterator() | |
const_iterator(typename Hash::const_iterator o) | |
const_iterator(const const_iterator &o) | |
const_iterator(const iterator &o) | |
bool | operator!=(const const_iterator &o) 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 &o) |
bool | operator==(const const_iterator &o) const |
Detailed Description
The QSet::const_iterator class provides an STL-style const iterator for QSet.
QSet 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.
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.
The default QSet::const_iterator constructor creates an uninitialized iterator. You must initialize it using a function like QSet::begin(), QSet::end(), or 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 generic algorithms. 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;
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.
See also QSet::iterator and QSetIterator.
Member Function Documentation
Synonyms for std::bidirectional_iterator_tag indicating these iterators are bidirectional iterators.
const_iterator::const_iterator()
Default constructs an instance of const_iterator.
const_iterator::const_iterator(typename Hash::const_iterator o)
Default constructs an instance of const_iterator.
const_iterator::const_iterator(const const_iterator &o)
Default constructs an instance of const_iterator.
const_iterator::const_iterator(const iterator &o)
Default constructs an instance of const_iterator.
bool const_iterator::operator!=(const const_iterator &o) const
const T &const_iterator::operator*() const
const_iterator const_iterator::operator+(int j) const
const_iterator &const_iterator::operator++()
const_iterator const_iterator::operator++(int)
const_iterator &const_iterator::operator+=(int j)
const_iterator const_iterator::operator-(int j) const
const_iterator &const_iterator::operator--()
const_iterator const_iterator::operator--(int)
const_iterator &const_iterator::operator-=(int j)
const T *const_iterator::operator->() const
const_iterator &const_iterator::operator=(const const_iterator &o)
Copy-assignment operator.