Iterator Class | Qt Core 6.4.3

- Qt 6.4
- Qt Core
- C++ Classes
- Iterator
- Qt 6.4.3 Reference Documentation

# Iterator Class

class QCborMap::Iterator

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

This class was introduced in Qt 5.12.

- List of all members, including inherited members

## Public Types

| iterator_category

## Public Functions

| Iterator(const Iterator &other)
| Iterator()
Iterator & | operator=(const Iterator &other)
QCborValue | key() const
QCborValueRef | value() const
bool | operator!=(const Iterator &other) const
bool | operator!=(const ConstIterator &other) const
value_type | operator*() const
Iterator | operator+(qsizetype j) const
Iterator & | operator++()
Iterator | operator++(int)
Iterator & | operator+=(qsizetype j)
Iterator | operator-(qsizetype j) const
qsizetype | operator-(Iterator j) const
Iterator & | operator--()
Iterator | operator--(int)
Iterator & | operator-=(qsizetype j)
const QCborValueConstRef * | operator->() const
bool | operator<(const Iterator &other) const
bool | operator<(const ConstIterator &other) const
bool | operator<=(const Iterator &other) const
bool | operator<=(const ConstIterator &other) const
bool | operator==(const Iterator &other) const
bool | operator==(const ConstIterator &other) const
bool | operator>(const Iterator &other) const
bool | operator>(const ConstIterator &other) const
bool | operator>=(const Iterator &other) const
bool | operator>=(const ConstIterator &other) const

## Detailed Description

QCborMap::Iterator allows you to iterate over a QCborMap and to modify the value (but not the key) stored under a particular key. If you want to iterate over a const QCborMap, you should use QCborMap::ConstIterator. It is generally good practice to use QCborMap::ConstIterator on a non-const QCborMap as well, unless you 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 once the object gets modified.

See also QCborMap::ConstIterator.

## Member Type Documentation

### Iterator::iterator_category

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

## Member Function Documentation

### bool Iterator::operator>=(const ConstIterator &other) const

### bool Iterator::operator>=(const Iterator &other) const

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

### bool Iterator::operator>(const ConstIterator &other) const

### bool Iterator::operator>(const Iterator &other) const

Returns `true` if the entry in the map pointed to by this iterator occurs after the entry pointed to by the other iterator.

### bool Iterator::operator<=(const ConstIterator &other) const

### bool Iterator::operator<=(const Iterator &other) const

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

### bool Iterator::operator<(const ConstIterator &other) const

### bool Iterator::operator<(const Iterator &other) const

Returns `true` if the entry in the map pointed to by this iterator occurs before the entry pointed to by the other iterator.

### bool Iterator::operator!=(const ConstIterator &other) const

### bool Iterator::operator!=(const Iterator &other) const

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

See also operator==().

### bool Iterator::operator==(const ConstIterator &other) const

### bool Iterator::operator==(const Iterator &other) const

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

See also operator!=().

### Iterator::Iterator(const Iterator &other)

Constructs an iterator as a copy of other.

### Iterator::Iterator()

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::begin() and QCborMap::end().

### Iterator &Iterator::operator=(const Iterator &other)

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

### QCborValue Iterator::key() const

Returns the current item's key.

There is no direct way of changing an item's key through an iterator, although it can be done by calling QCborMap::erase() followed by QCborMap::insert().

See also value().

### QCborValueRef Iterator::value() const

Returns a modifiable reference to the current item's value.

You can change the value for a key by using value() on the left side of an assignment.

The return value is of type QCborValueRef, a helper class for QCborArray and QCborMap. When you get an object of type QCborValueRef, you can use it as if it were a reference to a QCborValue. If you assign to it, the assignment will apply to the element in the QCborArray or QCborMap from which you got the reference.

See also key() and operator*().

### value_type Iterator::operator*() const

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

The second element of the pair is of type QCborValueRef, a helper class for QCborArray and QCborMap. When you get an object of type QCborValueRef, you can use it as if it were a reference to a QCborValue. If you assign to it, the assignment will apply to the element in the QCborArray or QCborMap from which you got the reference.

See also key() and value().

### Iterator Iterator::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-().

### Iterator &Iterator::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--().

### Iterator Iterator::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.

### Iterator &Iterator::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+().

### Iterator Iterator::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+().

### qsizetype Iterator::operator-(Iterator 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+().

### Iterator &Iterator::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++().

### Iterator Iterator::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.

### Iterator &Iterator::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 *Iterator::operator->() const

Returns a pointer to a modifiable reference to the current pair's value.