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

# QJsonObject Class

The QJsonObject class encapsulates a JSON object. More...

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

- List of all members, including inherited members
- QJsonObject is part of JSON Support in Qt and Implicitly Shared Classes.

This class is equality-comparable.

This class is equality-comparable with QJsonValue and QJsonValueConstRef.

Note: All functions in this class are reentrant.

## Public Types

class | const_iterator
class | iterator
| ConstIterator
| Iterator
| key_type
| mapped_type
| size_type

## Public Functions

| QJsonObject()
| QJsonObject(std::initializer_list<std::pair<QString, QJsonValue>> args)
| QJsonObject(const QJsonObject &other)
| QJsonObject(QJsonObject &&other)
| ~QJsonObject()
QJsonObject::iterator | begin()
QJsonObject::const_iterator | begin() const
QJsonObject::const_iterator | constBegin() const
QJsonObject::const_iterator | constEnd() const
QJsonObject::const_iterator | constFind(const QString &key) const
QJsonObject::const_iterator | constFind(QLatin1StringView key) const
QJsonObject::const_iterator | constFind(QStringView key) const
bool | contains(const QString &key) const
bool | contains(QLatin1StringView key) const
bool | contains(QStringView key) const
qsizetype | count() const
bool | empty() const
QJsonObject::iterator | end()
QJsonObject::const_iterator | end() const
QJsonObject::iterator | erase(QJsonObject::iterator it)
QJsonObject::iterator | find(const QString &key)
QJsonObject::iterator | find(QLatin1StringView key)
QJsonObject::iterator | find(QStringView key)
QJsonObject::const_iterator | find(QLatin1StringView key) const
QJsonObject::const_iterator | find(QStringView key) const
QJsonObject::const_iterator | find(const QString &key) const
QJsonObject::iterator | insert(const QString &key, const QJsonValue &value)
QJsonObject::iterator | insert(QLatin1StringView key, const QJsonValue &value)
QJsonObject::iterator | insert(QStringView key, const QJsonValue &value)
bool | isEmpty() const
QStringList | keys() const
qsizetype | length() const
void | remove(const QString &key)
void | remove(QLatin1StringView key)
void | remove(QStringView key)
qsizetype | size() const
void | swap(QJsonObject &other)
QJsonValue | take(const QString &key)
QJsonValue | take(QLatin1StringView key)
QJsonValue | take(QStringView key)
QVariantHash | toVariantHash() const
QVariantMap | toVariantMap() const
QJsonValue | value(const QString &key) const
QJsonValue | value(QLatin1StringView key) const
QJsonValue | value(QStringView key) const
QJsonObject & | operator=(QJsonObject &&other)
QJsonObject & | operator=(const QJsonObject &other)
QJsonValueRef | operator[](const QString &key)
QJsonValue | operator[](const QString &key) const
QJsonValueRef | operator[](QLatin1StringView key)
QJsonValueRef | operator[](QStringView key)
QJsonValue | operator[](QLatin1StringView key) const
QJsonValue | operator[](QStringView key) const

## Static Public Members

QJsonObject | fromVariantHash(const QVariantHash &hash)
QJsonObject | fromVariantMap(const QVariantMap &map)

## Related Non-Members

bool | operator!=(const QJsonObject &lhs, const QJsonObject &rhs)
bool | operator==(const QJsonObject &lhs, const QJsonObject &rhs)

## Detailed Description

A JSON object is a list of key value pairs, where the keys are unique strings and the values are represented by a QJsonValue.

A QJsonObject can be converted to and from a QVariantMap. You can query the number of (key, value) pairs with size(), insert(), and remove() entries from it and iterate over its content using the standard C++ iterator pattern.

QJsonObject is an implicitly shared class, and shares the data with the document it has been created from as long as it is not being modified.

You can convert the object to and from text based JSON through QJsonDocument.

See also JSON Support in Qt and Saving and Loading a Game.

## Member Type Documentation

### QJsonObject::ConstIterator

Qt-style synonym for QJsonObject::const_iterator.

### QJsonObject::Iterator

Qt-style synonym for QJsonObject::iterator.

### QJsonObject::key_type

Typedef for QString. Provided for STL compatibility.

### QJsonObject::mapped_type

Typedef for QJsonValue. Provided for STL compatibility.

### QJsonObject::size_type

Typedef for qsizetype. Provided for STL compatibility.

## Member Function Documentation

### QJsonObject::QJsonObject()

Constructs an empty JSON object.

See also isEmpty().

### QJsonObject::QJsonObject(std::initializer_list<std::pair<QString, QJsonValue>> args)

Constructs a QJsonObject instance initialized from args initialization list. For example:

     QJsonObject object
     {
         {"property1", 1},
         {"property2", 2}
     };

### `[noexcept]` QJsonObject::QJsonObject(const QJsonObject &other)

Creates a copy of other.

Since QJsonObject is implicitly shared, the copy is shallow as long as the object does not get modified.

### `[noexcept]` QJsonObject::QJsonObject(QJsonObject &&other)

Move-constructs a QJsonObject from other.

### `[noexcept]` QJsonObject::~QJsonObject()

Destroys the object.

### QJsonObject::iterator QJsonObject::begin()

Returns an STL-style iterator pointing to the first item in the object.

See also constBegin() and end().

### QJsonObject::const_iterator QJsonObject::begin() const

This is an overloaded function.

### QJsonObject::const_iterator QJsonObject::constBegin() const

Returns a const STL-style iterator pointing to the first item in the object.

See also begin() and constEnd().

### QJsonObject::const_iterator QJsonObject::constEnd() const

Returns a const STL-style iterator pointing to the imaginary item after the last item in the object.

See also constBegin() and end().

### QJsonObject::const_iterator QJsonObject::constFind(const QString &key) const

Returns a const iterator pointing to the item with key key in the map.

If the map contains no item with key key, the function returns constEnd().

### QJsonObject::const_iterator QJsonObject::constFind(QLatin1StringView key) const

This is an overloaded function.

### QJsonObject::const_iterator QJsonObject::constFind(QStringView key) const

This is an overloaded function.

### bool QJsonObject::contains(const QString &key) const

Returns `true` if the object contains key key.

See also insert(), remove(), and take().

### bool QJsonObject::contains(QLatin1StringView key) const

This is an overloaded function.

### bool QJsonObject::contains(QStringView key) const

This is an overloaded function.

### qsizetype QJsonObject::count() const

Same as size().

### bool QJsonObject::empty() const

This function is provided for STL compatibility. It is equivalent to isEmpty(), returning `true` if the object is empty; otherwise returning `false`.

### QJsonObject::iterator QJsonObject::end()

Returns an STL-style iterator pointing to the imaginary item after the last item in the object.

See also begin() and constEnd().

### QJsonObject::const_iterator QJsonObject::end() const

This is an overloaded function.

### QJsonObject::iterator QJsonObject::erase(QJsonObject::iterator it)

Removes the (key, value) pair pointed to by the iterator it from the map, and returns an iterator to the next item in the map.

See also remove().

### QJsonObject::iterator QJsonObject::find(const QString &key)

Returns an iterator pointing to the item with key key in the map.

If the map contains no item with key key, the function returns end().

### QJsonObject::iterator QJsonObject::find(QLatin1StringView key)

This is an overloaded function.

### QJsonObject::iterator QJsonObject::find(QStringView key)

This is an overloaded function.

### QJsonObject::const_iterator QJsonObject::find(QLatin1StringView key) const

This is an overloaded function.

### QJsonObject::const_iterator QJsonObject::find(QStringView key) const

This is an overloaded function.

### QJsonObject::const_iterator QJsonObject::find(const QString &key) const

This is an overloaded function.

### `[static]` QJsonObject QJsonObject::fromVariantHash(const QVariantHash &hash)

Converts the variant hash hash to a QJsonObject.

The keys in hash will be used as the keys in the JSON object, and the QVariant values will be converted to JSON values.

Note: Conversion from QVariant is not completely lossless. Please see the documentation in QJsonValue::fromVariant() for more information.

See also fromVariantMap(), toVariantHash(), and QJsonValue::fromVariant().

### `[static]` QJsonObject QJsonObject::fromVariantMap(const QVariantMap &map)

Converts the variant map map to a QJsonObject.

The keys in map will be used as the keys in the JSON object, and the QVariant values will be converted to JSON values.

Note: Conversion from QVariant is not completely lossless. Please see the documentation in QJsonValue::fromVariant() for more information.

See also fromVariantHash(), toVariantMap(), and QJsonValue::fromVariant().

### QJsonObject::iterator QJsonObject::insert(const QString &key, const QJsonValue &value)

Inserts a new item with the key key and a value of value.

If there is already an item with the key key, then that item's value is replaced with value.

Returns an iterator pointing to the inserted item.

If the value is QJsonValue::Undefined, it will cause the key to get removed from the object. The returned iterator will then point to end().

See also remove(), take(), QJsonObject::iterator, and end().

### QJsonObject::iterator QJsonObject::insert(QLatin1StringView key, const QJsonValue &value)

This is an overloaded function.

### QJsonObject::iterator QJsonObject::insert(QStringView key, const QJsonValue &value)

This is an overloaded function.

### bool QJsonObject::isEmpty() const

Returns `true` if the object is empty. This is the same as size() == 0.

See also size().

### QStringList QJsonObject::keys() const

Returns a list of all keys in this object.

The list is sorted alphabetically.

### qsizetype QJsonObject::length() const

Same as size().

### void QJsonObject::remove(const QString &key)

Removes key from the object.

See also insert() and take().

### void QJsonObject::remove(QLatin1StringView key)

This is an overloaded function.

### void QJsonObject::remove(QStringView key)

This is an overloaded function.

### qsizetype QJsonObject::size() const

Returns the number of (key, value) pairs stored in the object.

### `[noexcept]` void QJsonObject::swap(QJsonObject &other)

Swaps this object with other. This operation is very fast and never fails.

### QJsonValue QJsonObject::take(const QString &key)

Removes key from the object.

Returns a QJsonValue containing the value referenced by key. If key was not contained in the object, the returned QJsonValue is QJsonValue::Undefined.

See also insert(), remove(), and QJsonValue.

### QJsonValue QJsonObject::take(QLatin1StringView key)

This is an overloaded function.

### QJsonValue QJsonObject::take(QStringView key)

This is an overloaded function.

### QVariantHash QJsonObject::toVariantHash() const

Converts this object to a QVariantHash.

Returns the created hash.

See also toVariantMap().

### QVariantMap QJsonObject::toVariantMap() const

Converts this object to a QVariantMap.

Returns the created map.

See also toVariantHash().

### QJsonValue QJsonObject::value(const QString &key) const

Returns a QJsonValue representing the value for the key key.

The returned QJsonValue is QJsonValue::Undefined if the key does not exist.

See also QJsonValue and QJsonValue::isUndefined().

### QJsonValue QJsonObject::value(QLatin1StringView key) const

This is an overloaded function.

### QJsonValue QJsonObject::value(QStringView key) const

This is an overloaded function.

### `[noexcept]` QJsonObject &QJsonObject::operator=(QJsonObject &&other)

Move-assigns other to this object.

### `[noexcept]` QJsonObject &QJsonObject::operator=(const QJsonObject &other)

Assigns other to this object.

### QJsonValueRef QJsonObject::operator[](const QString &key)

Returns a reference to the value for key. If there is no value with key key in the object, one is created with a QJsonValue::Null value and then returned.

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

See also value().

### QJsonValue QJsonObject::operator[](const QString &key) const

Returns a QJsonValue representing the value for the key key.

This does the same as value().

The returned QJsonValue is QJsonValue::Undefined if the key does not exist.

See also value(), QJsonValue, and QJsonValue::isUndefined().

### QJsonValueRef QJsonObject::operator[](QLatin1StringView key)

This is an overloaded function.

### QJsonValueRef QJsonObject::operator[](QStringView key)

This is an overloaded function.

### QJsonValue QJsonObject::operator[](QLatin1StringView key) const

This is an overloaded function.

### QJsonValue QJsonObject::operator[](QStringView key) const

This is an overloaded function.

## Related Non-Members

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

Returns `true` if lhs object is not equal to rhs, `false` otherwise.

### `[noexcept]` bool operator==(const QJsonObject &lhs, const QJsonObject &rhs)

Returns `true` if lhs object is equal to rhs, `false` otherwise.