- Qt 6.8
- Qt Core
- C++ Classes
- ConstIterator
- Qt 6.8.1 Reference Documentation

# ConstIterator Class

class QCborMap::ConstIterator

The QCborMap::ConstIterator class provides an STL-style const iterator for QCborMap. More...

- List of all members, including inherited members
- ConstIterator is part of CBOR Support in Qt.

This class is strongly comparable.

This class is strongly comparable with Iterator.

## Public Types

| iterator_category

## Public Functions

| ConstIterator()
| ConstIterator(const QCborMap::ConstIterator &other)
QCborValue | key() const
QCborValueConstRef | value() const
QCborMap::ConstIterator::value_type | operator*() const
QCborMap::ConstIterator | operator+(qsizetype j) const
QCborMap::ConstIterator & | operator++()
QCborMap::ConstIterator | operator++(int)
QCborMap::ConstIterator & | operator+=(qsizetype j)
qsizetype | operator-(QCborMap::ConstIterator j) const
QCborMap::ConstIterator | operator-(qsizetype j) const
QCborMap::ConstIterator & | operator--()
QCborMap::ConstIterator | operator--(int)
QCborMap::ConstIterator & | operator-=(qsizetype j)
const QCborValueConstRef * | operator->() const
QCborMap::ConstIterator & | operator=(const QCborMap::ConstIterator &other)

## Related Non-Members

bool | operator!=(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)
bool | operator<(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)
bool | operator<=(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)
bool | operator==(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)
bool | operator>(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)
bool | operator>=(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)

## Detailed Description

QCborMap::ConstIterator allows you to iterate over a QCborMap. If you want to modify the QCborMap as you iterate over it, you must use QCborMap::Iterator instead. It is generally good practice to use QCborMap::ConstIterator, even on a non-const QCborMap, when you don't need to change the QCborMap through the iterator. Const iterators are slightly faster and improve code readability.

You must initialize the iterator using a QCborMap function like QCborMap::begin(), QCborMap::end(), or QCborMap::find() before you can start iterating..

Multiple iterators can be used on the same object. Existing iterators will however become dangling if the object gets modified.

See also QCborMap::Iterator.

## Member Type Documentation

### ConstIterator::iterator_category

A synonym for std::random_access_iterator_tag indicating this iterator is a random-access iterator.

## Member Function Documentation

### `[constexpr noexcept]` ConstIterator::ConstIterator()

Constructs an uninitialized iterator.

Functions like key(), value(), and operator++() must not be called on an uninitialized iterator. Use operator=() to assign a value to it before using it.

See also QCborMap::constBegin() and QCborMap::constEnd().

### `[constexpr noexcept]` ConstIterator::ConstIterator(const QCborMap::ConstIterator &other)

Constructs an iterator as a copy of other.

### QCborValue ConstIterator::key() const

Returns the current item's key.

See also value().

### QCborValueConstRef ConstIterator::value() const

Returns the current item's value.

See also key() and operator*().

### QCborMap::ConstIterator::value_type ConstIterator::operator*() const

Returns a pair containing the current item's key and value.

See also key() and value().

### QCborMap::ConstIterator ConstIterator::operator+(qsizetype j) const

Returns an iterator to the item at j positions forward from this iterator. If j is negative, the iterator goes backward.

See also operator-().

### QCborMap::ConstIterator &ConstIterator::operator++()

The prefix `++` operator, `++i`, advances the iterator to the next item in the map and returns this iterator.

Calling this function on QCborMap::end() leads to undefined results.

See also operator--().

### QCborMap::ConstIterator ConstIterator::operator++(int)

This is an overloaded function.

The postfix `++` operator, `i++`, advances the iterator to the next item in the map and returns an iterator to the previously current item.

### QCborMap::ConstIterator &ConstIterator::operator+=(qsizetype j)

Advances the iterator by j items. If j is negative, the iterator goes backward. Returns a reference to this iterator.

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

### qsizetype ConstIterator::operator-(QCborMap::ConstIterator j) const

Returns the position of the item at iterator j relative to the item at this iterator. If the item at j is forward of this time, the returned value is negative.

See also operator+().

### QCborMap::ConstIterator ConstIterator::operator-(qsizetype j) const

Returns an iterator to the item at j positions backward from this iterator. If j is negative, the iterator goes forward.

See also operator+().

### QCborMap::ConstIterator &ConstIterator::operator--()

The prefix `--` operator, `--i`, makes the preceding item current and returns this iterator.

Calling this function on QCborMap::begin() leads to undefined results.

See also operator++().

### QCborMap::ConstIterator ConstIterator::operator--(int)

This is an overloaded function.

The postfix `--` operator, `i--`, makes the preceding item current and returns an iterator pointing to the previously current item.

### QCborMap::ConstIterator &ConstIterator::operator-=(qsizetype j)

Makes the iterator go back by j items. If j is negative, the iterator goes forward. Returns a reference to this iterator.

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

### const QCborValueConstRef *ConstIterator::operator->() const

Returns a pointer to the current pair's value.

### QCborMap::ConstIterator &ConstIterator::operator=(const QCborMap::ConstIterator &other)

Makes this iterator a copy of other and returns a reference to this iterator.

## Related Non-Members

### `[noexcept]` bool operator!=(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)

Returns `true` if lhs points to a different entry in the map than rhs iterator; otherwise returns `false`.

See also operator==().

### `[noexcept]` bool operator<(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)

Returns `true` if the entry in the map pointed to by lhs iterator occurs before the entry pointed to by the rhs iterator.

### `[noexcept]` bool operator<=(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)

Returns `true` if the entry in the map pointed to by lhs iterator occurs before or is the same entry as is pointed to by the rhs iterator.

### `[noexcept]` bool operator==(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)

Returns `true` if lhs points to the same entry in the map as rhs iterator; otherwise returns `false`.

See also operator!=().

### `[noexcept]` bool operator>(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)

Returns `true` if the entry in the map pointed to by lhs iterator occurs after the entry pointed to by the rhs iterator.

### `[noexcept]` bool operator>=(const QCborMap::ConstIterator &lhs, const QCborMap::ConstIterator &rhs)

Returns `true` if the entry in the map pointed to by lhs iterator occurs after or is the same entry as is pointed to by the rhs iterator.