iterator Classclass QSet::iterator
This class was introduced in Qt 4.2.
|iterator(const iterator &other)|
|iterator &||operator=(const iterator &other)|
|bool||operator!=(const iterator &other) const|
|bool||operator!=(const const_iterator &other) const|
|const T &||operator*() const|
|const T *||operator->() const|
|bool||operator==(const iterator &other) const|
|bool||operator==(const const_iterator &other) const|
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<T>::iterator allows you to iterate over a QSet and to remove items (using QSet::erase()) while you iterate. (QSet doesn't let you modify a value through an iterator, because that would potentially require moving the value in the internal hash table used by QSet.) If you want to iterate over a const QSet, you should use QSet::const_iterator. 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::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:
Here's a loop that removes certain items (all those that start with 'J') from a set while iterating:
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:
Multiple iterators can be used on the same set.
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.
Member Type Documentation
Synonyms for std::bidirectional_iterator_tag indicating these iterators are bidirectional iterators.
Member Function Documentation
This is an overloaded function.
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.
bool iterator::operator!=(const iterator &other) const
true if other points to a different item than this iterator; otherwise returns
See also operator==().
bool iterator::operator!=(const const_iterator &other) const
bool iterator::operator==(const const_iterator &other) const
This is an overloaded function.
bool iterator::operator==(const iterator &other) const
true if other points to the same item as this iterator; otherwise returns
See also operator!=().
Returns a pointer to the current item.
See also operator*().
Returns a reference to the current item.
See also operator->().
Assigns other to this iterator.
iterator::iterator(const iterator &other)
Constructs a copy of other.
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.
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