Contents

• Public Functions
• Detailed Description

Detailed Description

TheQMutableLinkedListIterator class provides a Java-style non-const iterator forQLinkedList.

QLinkedList has bothJava-style iterators andSTL-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.

QMutableLinkedListIterator<T> allows you to iterate over aQLinkedList<T> and modify the list. If you don't want to modify the list (or have a constQLinkedList), use the slightly fasterQLinkedListIterator<T> instead.

TheQMutableLinkedListIterator constructor takes aQLinkedList 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;...QMutableLinkedListIterator<float> i(list);while (i.hasNext())qDebug()<< i.next();

Thenext() function returns the next item in the list and advances the iterator. Unlike STL-style iterators, Java-style iterators pointbetween items rather than directlyat items. The first call tonext() advances the iterator to the position between the first and second item, and returns the first item; the second call tonext() 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:

QMutableLinkedListIterator<float> i(list);i.toBack();while (i.hasPrevious())qDebug()<< i.previous();

If you want to find all occurrences of a particular value, usefindNext() orfindPrevious() in a loop.

If you want to remove items as you iterate over the list, useremove(). If you want to modify the value of an item, usesetValue(). If you want to insert a new item in the list, useinsert().

Example:

QMutableLinkedListIterator<int> i(list);while (i.hasNext()) {int val= i.next();if (val<0) {        i.setValue(-val);    }elseif (val==0) {        i.remove();    }}

The example traverses a list, replacing negative numbers with their absolute values, and eliminating zeroes.

Only one mutable iterator can be active on a given list at any time. Furthermore, no changes should be done directly to the list while the iterator is active (as opposed to through the iterator), since this could invalidate the iterator and lead to undefined behavior.

Member Function Documentation

QMutableLinkedListIterator::QMutableLinkedListIterator(QLinkedList<T> & list)

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

See alsooperator=().

QMutableLinkedListIterator::~QMutableLinkedListIterator()

Destroys the iterator.

See alsooperator=().

bool QMutableLinkedListIterator::findNext(constT & value)

Searches forvalue starting from the current iterator position forward. Returns true ifvalue is found; otherwise returns false.

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

See alsofindPrevious().

bool QMutableLinkedListIterator::findPrevious(constT & value)

Searches forvalue starting from the current iterator position backward. Returns true ifvalue is found; otherwise returns false.

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

See alsofindNext().

bool QMutableLinkedListIterator::hasNext() const

Returns true if there is at least one item ahead of the iterator, i.e. the iterator isnot at the back of the container; otherwise returns false.

See alsohasPrevious() andnext().

bool QMutableLinkedListIterator::hasPrevious() const

Returns true if there is at least one item behind the iterator, i.e. the iterator isnot at the front of the container; otherwise returns false.

See alsohasNext() andprevious().

void QMutableLinkedListIterator::insert(constT & value)

Insertsvalue at the current iterator position. After the call, the iterator is located just after the inserted item.

See alsoremove() andsetValue().

T & QMutableLinkedListIterator::next()

Returns a reference to 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 alsohasNext(),peekNext(), andprevious().

T & QMutableLinkedListIterator::peekNext() const

Returns a reference to 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 alsohasNext(),next(), andpeekPrevious().

T & QMutableLinkedListIterator::peekPrevious() const

Returns a reference to 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 alsohasPrevious(),previous(), andpeekNext().

T & QMutableLinkedListIterator::previous()

Returns a reference to 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 alsohasPrevious(),peekPrevious(), andnext().

void QMutableLinkedListIterator::remove()

Removes the last item that was jumped over using one of the traversal functions (next(),previous(),findNext(),findPrevious()).

Example:

QMutableLinkedListIterator<int> i(list);while (i.hasNext()) {int val= i.next();if (val<-32768|| val>32767)        i.remove();}

See alsoinsert() andsetValue().

void QMutableLinkedListIterator::setValue(constT & value) const

Replaces the value of the last item that was jumped over using one of the traversal functions withvalue.

The traversal functions arenext(),previous(),findNext(), andfindPrevious().

Example:

QMutableLinkedListIterator<double> i(list);while (i.hasNext()) {double val= i.next();    i.setValue(sqrt(val));}

See alsovalue(),remove(), andinsert().

void QMutableLinkedListIterator::toBack()

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

See alsotoFront() andprevious().

void QMutableLinkedListIterator::toFront()

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

See alsotoBack() andnext().

constT & QMutableLinkedListIterator::value() const

Returns the value of the last item that was jumped over using one of the traversal functions (next(),previous(),findNext(),findPrevious()).

After a call tonext() orfindNext(), value() is equivalent topeekPrevious(). After a call toprevious() orfindPrevious(), value() is equivalent topeekNext().

See alsosetValue().

T & QMutableLinkedListIterator::value()

This is an overloaded function.

Returns a non-const reference to the value of the last item that was jumped over using one of the traversal functions.

QMutableLinkedListIterator & QMutableLinkedListIterator::operator=(QLinkedList<T> & list)

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

See alsotoFront() andtoBack().