Qt Documentation

Qt 5.14
Qt Core
C++ Classes
QLinkedListIterator

QLinkedListIterator Class

The QLinkedListIterator class provides a Java-style const iterator for QLinkedList. More...

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

List of all members, including inherited members

Public Functions

	QLinkedListIterator(const QLinkedList<T> &list)
QLinkedListIterator<T> &	operator=(const QLinkedList<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

QLinkedList has 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.

QLinkedListIterator<T> allows you to iterate over a QLinkedList<T>. If you want to modify the list as you iterate over it, use QMutableLinkedListIterator<T> instead.

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

QLinkedList<float> list;
...
QLinkedListIterator<float> i(list);
while (i.hasNext())
    qDebug() << i.next();

The next() function returns the next item in the list 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, and returns the second item; and so on.

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

QLinkedListIterator<float> i(list);
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 list. If the list is modified while a QLinkedListIterator is active, the QLinkedListIterator will continue iterating over the original list, ignoring the modified copy.

Member Function Documentation

bool QLinkedListIterator::findPrevious(const T &value)

Searches for value starting from the current iterator position backward. Returns true if value is found; otherwise returns false.

After the call, if value was found, the iterator is positioned just before the matching item; otherwise, the iterator is positioned at the front of the container.

See also findNext().

bool QLinkedListIterator::findNext(const T &value)

Searches for value starting from the current iterator position forward. Returns true if value is found; otherwise returns false.

After the call, if value was found, the iterator is positioned just after the matching item; otherwise, the iterator is positioned at the back of the container.

See also findPrevious().

const T &QLinkedListIterator::peekPrevious() const

Returns the previous item without moving the iterator.

Calling this function on an iterator located at the front of the container leads to undefined results.

See also hasPrevious(), previous(), and peekNext().

const T &QLinkedListIterator::previous()

Returns the previous item and moves the iterator back by one position.

Calling this function on an iterator located at the front of the container leads to undefined results.

See also hasPrevious(), peekPrevious(), and next().

bool QLinkedListIterator::hasPrevious() const

Returns true if there is at least one item behind the iterator, i.e. the iterator is not at the front of the container; otherwise returns false.

See also hasNext() and previous().

const T &QLinkedListIterator::peekNext() const

Returns the next item without moving the iterator.

Calling this function on an iterator located at the back of the container leads to undefined results.

See also hasNext(), next(), and peekPrevious().

const T &QLinkedListIterator::next()

Returns the next item and advances the iterator by one position.

Calling this function on an iterator located at the back of the container leads to undefined results.

See also hasNext(), peekNext(), and previous().

bool QLinkedListIterator::hasNext() const

Returns true if there is at least one item ahead of the iterator, i.e. the iterator is not at the back of the container; otherwise returns false.

See also hasPrevious() and next().

void QLinkedListIterator::toBack()

Moves the iterator to the back of the container (after the last item).

See also toFront() and previous().

void QLinkedListIterator::toFront()

Moves the iterator to the front of the container (before the first item).

See also toBack() and next().

QLinkedListIterator<T> &QLinkedListIterator::operator=(const QLinkedList<T> &container)

Makes the iterator operate on list. The iterator is set to be at the front of the list (before the first item).

See also toFront() and toBack().

QLinkedListIterator::QLinkedListIterator(const QLinkedList<T> &list)

Constructs an iterator for traversing list. The iterator is set to be at the front of the list (before the first item).

See also operator=().

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