- Qt 5.15
- Qt Core
- C++ Classes
- const_iterator
- Qt 5.15.15 Reference Documentation

# const_iterator Class

class QJsonArray::const_iterator

The QJsonArray::const_iterator class provides an STL-style const iterator for QJsonArray. More...

- List of all members, including inherited members

## Public Types

typedef | iterator_category

## Public Functions

| const_iterator(const iterator &other)
| const_iterator(const const_iterator &other)
| const_iterator()
bool | operator!=(const const_iterator &other) const
QJsonValue | operator*() const
const_iterator | operator+(int j) const
const_iterator & | operator++()
const_iterator | operator++(int)
const_iterator & | operator+=(int j)
const_iterator | operator-(int j) const
int | operator-(const_iterator other) const
const_iterator & | operator--()
const_iterator | operator--(int)
const_iterator & | operator-=(int j)
QJsonValue * | operator->() const
bool | operator<(const const_iterator &other) const
bool | operator<=(const const_iterator &other) const
bool | operator==(const const_iterator &other) const
bool | operator>(const const_iterator &other) const
bool | operator>=(const const_iterator &other) const
QJsonValue | operator[](int j) const

## Detailed Description

QJsonArray::const_iterator allows you to iterate over a QJsonArray. If you want to modify the QJsonArray as you iterate over it, use QJsonArray::iterator instead. It is generally a good practice to use QJsonArray::const_iterator on a non-const QJsonArray as well, unless you need to change the QJsonArray through the iterator. Const iterators are slightly faster and improves code readability.

The default QJsonArray::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QJsonArray function like QJsonArray::constBegin(), QJsonArray::constEnd(), or QJsonArray::insert() before you can start iterating.

Most QJsonArray functions accept an integer index rather than an iterator. For that reason, iterators are rarely useful in connection with QJsonArray. One place where STL-style iterators do make sense is as arguments to generic algorithms.

Multiple iterators can be used on the same array. However, be aware that any non-const function call performed on the QJsonArray will render all existing iterators undefined.

See also QJsonArray::iterator.

## Member Type Documentation

### typedef const_iterator::iterator_category

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

## Member Function Documentation

### const_iterator::const_iterator(const iterator &other)

Constructs a copy of other.

### const_iterator::const_iterator(const const_iterator &other)

Constructs a copy of other.

### const_iterator::const_iterator()

Constructs an uninitialized iterator.

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

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

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

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

See also operator==().

### QJsonValue const_iterator::operator*() const

Returns the current item.

### const_iterator const_iterator::operator+(int 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-() and operator+=().

### const_iterator &const_iterator::operator++()

The prefix ++ operator, `++it`, advances the iterator to the next item in the array and returns an iterator to the new current item.

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

See also operator--().

### const_iterator const_iterator::operator++(int)

This is an overloaded function.

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

### const_iterator &const_iterator::operator+=(int j)

Advances the iterator by j items. If j is negative, the iterator goes backward.

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

### const_iterator const_iterator::operator-(int 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+() and operator-=().

### int const_iterator::operator-(const_iterator other) const

Returns the number of items between the item pointed to by other and the item pointed to by this iterator.

### const_iterator &const_iterator::operator--()

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

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

See also operator++().

### const_iterator const_iterator::operator--(int)

This is an overloaded function.

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

### const_iterator &const_iterator::operator-=(int j)

Makes the iterator go back by j items. If j is negative, the iterator goes forward.

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

### QJsonValue *const_iterator::operator->() const

Returns a pointer to the current item.

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

Returns `true` if the item pointed to by this iterator is less than the item pointed to by the other iterator.

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

Returns `true` if the item pointed to by this iterator is less than or equal to the item pointed to by the other iterator.

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

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

See also operator!=().

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

Returns `true` if the item pointed to by this iterator is greater than the item pointed to by the other iterator.

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

Returns `true` if the item pointed to by this iterator is greater than or equal to the item pointed to by the other iterator.

### QJsonValue const_iterator::operator[](int j) const

Returns the item at offset j from the item pointed to by this iterator (the item at position `*this + j`).

This function is provided to make QJsonArray iterators behave like C++ pointers.

See also operator+().