QJsonObject Class | Qt Core 5.6

Qt 5.6 | Qt Core | C++ Classes | QJsonObject

Qt 5.6.2 Reference Documentation

# QJsonObject Class

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

Header: | #include <QJsonObject>
qmake: | QT += core
Since: | Qt 5.0

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Types

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

## Public Functions

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

## Static Public Members

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

## Detailed Description

The QJsonObject class encapsulates a JSON object.

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 JSON Save Game Example.

## Member Type Documentation

### typedef QJsonObject::ConstIterator

Qt-style synonym for QJsonObject::const_iterator.

### typedef QJsonObject::Iterator

Qt-style synonym for QJsonObject::iterator.

### typedef QJsonObject::key_type

Typedef for QString. Provided for STL compatibility.

### typedef QJsonObject::mapped_type

Typedef for QJsonValue. Provided for STL compatibility.

### typedef QJsonObject::size_type

Typedef for int. Provided for STL compatibility.

## Member Function Documentation

### QJsonObject::QJsonObject()

Constructs an empty JSON object.

See also isEmpty().

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

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

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

This function was introduced in Qt 5.4.

### 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.

### QJsonObject::~QJsonObject()

Destroys the object.

### iterator QJsonObject::begin()

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

See also constBegin() and end().

### const_iterator QJsonObject::begin() const

This is an overloaded function.

### const_iterator QJsonObject::constBegin() const

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

See also begin() and constEnd().

### 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().

### 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().

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

Returns `true` if the object contains key key.

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

### int QJsonObject::count() const

This is an overloaded function.

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`.

### 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().

### const_iterator QJsonObject::end() const

This is an overloaded function.

### iterator QJsonObject::erase(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().

### 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().

### 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.

This function was introduced in Qt 5.5.

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.

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

### 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().

### 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 lexographically.

### int QJsonObject::length() const

This is an overloaded function.

Same as size().

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

Removes key from the object.

See also insert() and take().

### int QJsonObject::size() const

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

### 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.

### QVariantHash QJsonObject::toVariantHash() const

Converts this object to a QVariantHash.

Returns the created hash.

This function was introduced in Qt 5.5.

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().

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

Returns `true` if other is not equal to this object.

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

Assigns other to this object.

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

Returns `true` if other is equal to this object.

### 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[](const QString &key)

Returns a reference to the value for key.

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().