W3cubDocs

/Qt 5.13

const_iterator Class

Class const_iterator is declared in class QJsonObject.

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

This class was introduced in Qt 5.0.

Public Types

typedef iterator_category

Public Functions

const_iterator(const iterator &other)
const_iterator()
QString key() const
QJsonValue value() const
bool operator!=(const const_iterator &other) const
bool operator!=(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
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 iterator &other) const

Detailed Description

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

The default QJsonObject::const_iterator constructor creates an uninitialized iterator. You must initialize it using a QJsonObject function like QJsonObject::constBegin(), QJsonObject::constEnd(), or QJsonObject::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 QJsonObject::iterator, JSON Support in Qt, and JSON Save Game Example.

Member Type Documentation

typedef const_iterator::iterator_category

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

Note: In Qt versions before 5.6, this was set by mistake to std::bidirectional_iterator_tag.

Member Function Documentation

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

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

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

See also operator==().

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

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

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

See also operator!=().

const_iterator::const_iterator(const iterator &other)

Constructs a copy of other.

const_iterator::const_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 QJsonObject::constBegin() and QJsonObject::constEnd().

QString const_iterator::key() const

Returns the current item's key.

See also value().

QJsonValue const_iterator::value() const

Returns the current item's value.

See also key() and operator*().

QJsonValue const_iterator::operator*() const

Returns the current item's value.

Same as value().

See also key().

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.

This operation can be slow for large j values.

See also operator-().

const_iterator &const_iterator::operator++()

The prefix ++ operator, ++i, advances the iterator to the next item in the object and returns an iterator to the new current item.

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

See also operator--().

const_iterator const_iterator::operator++(int)

This is an overloaded function.

The postfix ++ operator, i++, advances the iterator to the next item in the object 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.

This operation can be slow for large j values.

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.

This operation can be slow for large j values.

See also operator+().

const_iterator &const_iterator::operator--()

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

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

See also operator++().

const_iterator const_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.

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

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

This operation can be slow for large j values.

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

QJsonValue *const_iterator::operator->() const

Returns a pointer to the current item.

© The Qt Company Ltd
Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-5.13/qjsonobject-const-iterator.html