- Qt 6.9
- Qt Core
- C++ Classes
- QTaggedIterator
- Qt 6.9.3 Reference Documentation

# QTaggedIterator Class

template <typename Iterator, typename IteratorCategory> class QTaggedIterator

QTaggedIterator is a template class that wraps an iterator and exposes standard iterator traits. More...

Header: | `#include <QTaggedIterator>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake: | `QT += core`
Since: | Qt 6.0

- List of all members, including inherited members

## Public Functions

| QTaggedIterator(Iterator &&it)
bool | operator!=(const QTaggedIterator<Iterator, IteratorCategory> &other) const
QTaggedIterator<Iterator, IteratorCategory> | operator+(qsizetype j) const
QTaggedIterator<Iterator, IteratorCategory> & | operator++()
QTaggedIterator<Iterator, IteratorCategory> | operator++(int x)
QTaggedIterator<Iterator, IteratorCategory> & | operator+=(qsizetype j)
qsizetype | operator-(const QTaggedIterator<Iterator, IteratorCategory> &j) const
QTaggedIterator<Iterator, IteratorCategory> | operator-(qsizetype j) const
QTaggedIterator<Iterator, IteratorCategory> & | operator--()
QTaggedIterator<Iterator, IteratorCategory> | operator--(int x)
QTaggedIterator<Iterator, IteratorCategory> & | operator-=(qsizetype j)
bool | operator==(const QTaggedIterator<Iterator, IteratorCategory> &other) const

## Related Non-Members

QTaggedIterator<Iterator, IteratorCategory> | operator+(qsizetype j, const QTaggedIterator<Iterator, IteratorCategory> &k)

## Detailed Description

In order to use an iterator any of the standard algorithms, its iterator traits need to be known. As QSequentialIterable can work with many different kinds of containers, we cannot declare the traits in the iterator classes themselves. A QTaggedIterator gives you a way to explicitly declare a trait for a concrete instance of an iterator or QConstIterator.

## Member Function Documentation

### QTaggedIterator::QTaggedIterator(Iterator &&it)

Constructs a QTaggedIterator from an iterator or QConstIterator it. Checks whether the IteratorCategory passed as template argument matches the run time capabilities of it; if there's no match, it is refused.

### bool QTaggedIterator::operator!=(const QTaggedIterator<Iterator, IteratorCategory> &other) const

Returns `true` if other points to a different item than this iterator; otherwise returns `false`.

See also operator==().

### QTaggedIterator<Iterator, IteratorCategory> QTaggedIterator::operator+(qsizetype j) const

Returns an iterator to the item at j positions forward from this iterator.

See also operator-() and operator+=().

### QTaggedIterator<Iterator, IteratorCategory> &QTaggedIterator::operator++()

The prefix `++` operator (`++it`) advances the iterator to the next item in the container and returns an iterator to the new current item.

Calling this function on QSequentialIterable::constEnd() leads to undefined results.

See also operator--().

### QTaggedIterator<Iterator, IteratorCategory> QTaggedIterator::operator++(int x)

The postfix `++` operator (`it++`) advances the iterator to the next item in the container and returns an iterator to the previously current item.

This is an overloaded function.

### QTaggedIterator<Iterator, IteratorCategory> &QTaggedIterator::operator+=(qsizetype j)

Advances the iterator by j items.

See also operator-=() and operator+().

### qsizetype QTaggedIterator::operator-(const QTaggedIterator<Iterator, IteratorCategory> &j) const

Returns the distance between this iterator and j.

See also operator+(), operator-=(), and QIterable::canReverseIterate().

### QTaggedIterator<Iterator, IteratorCategory> QTaggedIterator::operator-(qsizetype j) const

Returns an iterator to the item at j positions backward from this iterator.

If the container in the QVariant does not support bi-directional iteration, calling this function leads to undefined results.

See also operator+(), operator-=(), and QIterable::canReverseIterate().

### QTaggedIterator<Iterator, IteratorCategory> &QTaggedIterator::operator--()

The prefix `--` operator (`--it`) makes the preceding item current and returns an iterator to the new current item.

Calling this function on QSequentialIterable::constBegin() leads to undefined results.

If the container in the QVariant does not support bi-directional iteration, calling this function leads to undefined results.

See also operator++() and QIterable::canReverseIterate().

### QTaggedIterator<Iterator, IteratorCategory> QTaggedIterator::operator--(int x)

The postfix `--` operator (`it--`) makes the preceding item current and returns an iterator to the previously current item.

If the container in the QVariant does not support bi-directional iteration, calling this function leads to undefined results.

This is an overloaded function.

See also QIterable::canReverseIterate().

### QTaggedIterator<Iterator, IteratorCategory> &QTaggedIterator::operator-=(qsizetype j)

Makes the iterator go back by j items.

If the container in the QVariant does not support bi-directional iteration, calling this function leads to undefined results.

See also operator+=(), operator-(), and QIterable::canReverseIterate().

### bool QTaggedIterator::operator==(const QTaggedIterator<Iterator, IteratorCategory> &other) const

Returns `true` if other points to the same item as this iterator; otherwise returns `false`.

See also operator!=().

## Related Non-Members

### QTaggedIterator<Iterator, IteratorCategory> operator+(qsizetype j, const QTaggedIterator<Iterator, IteratorCategory> &k)

Returns an iterator to the item at j positions forward from iterator k.