QSetIterator Class

The QSetIterator class provides a Java-style const iterator for QSet. More...

Header: #include <QSetIterator>
qmake: QT += core

Public Functions

QSetIterator(const QSet<T> &set)
QSetIterator<T> &operator=(const QSet<T> &container)
bool findNext(const T &value)
bool findPrevious(const T &value)
bool hasNext() const
bool hasPrevious() const
const T &next()
const T &peekNext() const
const T &peekPrevious() const
const T &previous()
void toBack()
void toFront()

Detailed Description

QSet supports both Java-style iterators and STL-style iterators. The Java-style iterators are more high-level and easier to use than the STL-style iterators; on the other hand, they are slightly less efficient.

QSetIterator<T> allows you to iterate over a QSet<T>. If you want to modify the set as you iterate over it, use QMutableSetIterator<T> instead.

The constructor takes a QSet as argument. After construction, the iterator is located at the very beginning of the set (before the first item). Here's how to iterate over all the elements sequentially:

QSet<QString> set;
...
QSetIterator<QString> i(set);
while (i.hasNext())
    qDebug() << i.next();

The next() function returns the next item in the set and advances the iterator. Unlike STL-style iterators, Java-style iterators point between items rather than directly at items. The first call to next() advances the iterator to the position between the first and second item, and returns the first item; the second call to next() advances the iterator to the position between the second and third item, returning the second item; and so on.

Here's how to iterate over the elements in reverse order:

QSetIterator<QString> i(set);
i.toBack();
while (i.hasPrevious())
    qDebug() << i.previous();

If you want to find all occurrences of a particular value, use findNext() or findPrevious() in a loop.

Multiple iterators can be used on the same set. If the set is modified while a QSetIterator is active, the QSetIterator will continue iterating over the original set, ignoring the modified copy.

See also QMutableSetIterator and QSet::const_iterator.

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