QJsonValue Class

QJsonValue Class

The QJsonValue class encapsulates a value in JSON. More...

#include <QJsonValue>

Note: All functions in this class are reentrant.

This class was introduced in QtCore 5.0.

• List of all members, including inherited members

Public Types

enum	Type { Null, Bool, Double, String, ..., Undefined }

Public Functions

	QJsonValue(Type type = Null)
	QJsonValue(bool b)
	QJsonValue(double n)
	QJsonValue(const QString & s)
	QJsonValue(QLatin1String s)
	QJsonValue(const QJsonArray & a)
	QJsonValue(const QJsonObject & o)
	QJsonValue(const QJsonValue & other)
	QJsonValue(int n)
	~QJsonValue()
bool	isArray() const
bool	isBool() const
bool	isDouble() const
bool	isNull() const
bool	isObject() const
bool	isString() const
bool	isUndefined() const
QJsonArray	toArray(const QJsonArray & defaultValue) const
QJsonArray	toArray() const
bool	toBool(bool defaultValue = false) const
double	toDouble(double defaultValue = 0) const
QJsonObject	toObject(const QJsonObject & defaultValue) const
QJsonObject	toObject() const
QString	toString(const QString & defaultValue = QString()) const
QVariant	toVariant() const
Type	type() const
bool	operator!=(const QJsonValue & other) const
QJsonValue &	operator=(const QJsonValue & other)
bool	operator==(const QJsonValue & other) const

Static Public Members

QJsonValue

fromVariant(const QVariant & variant)

Detailed Description

The QJsonValue class encapsulates a value in JSON.

A value in JSON can be one of 6 basic types:

JSON is a format to store structured data. It has 6 basic data types:

• bool QJsonValue::Bool
• double QJsonValue::Double
• string QJsonValue::String
• array QJsonValue::Array
• object QJsonValue::Object
• null QJsonValue::Null

A value can represent any of the above data types. In addition, QJsonValue has one special flag to represent undefined values. This can be queried with isUndefined().

The type of the value can be queried with type() or accessors like isBool(), isString(), and so on. Likewise, the value can be converted to the type stored in it using the toBool(), toString() and so on.

Values are strictly typed internally and contrary to QVariant will not attempt to do any implicit type conversions. This implies that converting to a type that is not stored in the value will return a default constructed return value.

Member Type Documentation

enum QJsonValue::Type

This enum describes the type of the JSON value.

Constant	Value	Description
QJsonValue::Null	0x0	A Null value
QJsonValue::Bool	0x1	A boolean value. Use toBool() to convert to a bool.
QJsonValue::Double	0x2	A double. Use toDouble() to convert to a double.
QJsonValue::String	0x3	A string. Use toString() to convert to a QString.
QJsonValue::Array	0x4	An array. Use toArray() to convert to a QJsonArray.
QJsonValue::Object	0x5	An object. Use toObject() to convert to a QJsonObject.
QJsonValue::Undefined	0x80	The value is undefined. This is usually returned as an error condition, when trying to read an out of bounds value in an array or a non existent key in an object.

Member Function Documentation

QJsonValue::QJsonValue(Type type = Null)

Creates a QJsonValue of type type.

The default is to create a Null value.

QJsonValue::QJsonValue(bool b)

Creates a value of type Bool, with value b.

QJsonValue::QJsonValue(double n)

Creates a value of type Double, with value n.

QJsonValue::QJsonValue(const QString & s)

Creates a value of type String, with value s.

QJsonValue::QJsonValue(QLatin1String s)

Creates a value of type String, with value s.

QJsonValue::QJsonValue(const QJsonArray & a)

Creates a value of type Array, with value a.

QJsonValue::QJsonValue(const QJsonObject & o)

Creates a value of type Object, with value o.

QJsonValue::QJsonValue(const QJsonValue & other)

Creates a copy of other.

QJsonValue::QJsonValue(int n)

This is an overloaded function.

Creates a value of type Double, with value n.

QJsonValue::~QJsonValue()

Destroys the value.

QJsonValue QJsonValue::fromVariant(const QVariant & variant) [static]

Converts variant to a QJsonValue and returns it.

The conversion will convert QVariant types as follows:

• QVariant::Bool(obsolete) to Bool
• QVariant::Int(obsolete)
• QVariant::Double(obsolete)
• QVariant::LongLong(obsolete)
• QVariant::ULongLong(obsolete)
• QVariant::UInt(obsolete) to Double
• QVariant::String(obsolete) to String
• QVariant::StringList(obsolete)
• QVariant::VariantList to Array
• QVariant::VariantMap to Object

For all other QVariant types a conversion to a QString will be attempted. If the returned string is empty, a NullQJsonValue will be stored, otherwise a String value using the returned QString.

See also toVariant().

bool QJsonValue::isArray() const

Returns true if the value contains an array.

See also toArray().

bool QJsonValue::isBool() const

Returns true if the value contains a boolean.

See also toBool().

bool QJsonValue::isDouble() const

Returns true if the value contains a double.

See also toDouble().

bool QJsonValue::isNull() const

Returns true if the value is null.

bool QJsonValue::isObject() const

Returns true if the value contains an object.

See also toObject().

bool QJsonValue::isString() const

Returns true if the value contains a string.

See also toString().

bool QJsonValue::isUndefined() const

Returns true if the value is undefined. This can happen in certain error cases as e.g. accessing a non existing key in aQJsonObject.

QJsonArray QJsonValue::toArray(const QJsonArray & defaultValue) const

Converts the value to an array and returns it.

If type() is not Array, the defaultValue will be returned.

QJsonArray QJsonValue::toArray() const

This is an overloaded function.

Converts the value to an array and returns it.

If type() is not Array, a QJsonArray() will be returned.

bool QJsonValue::toBool(bool defaultValue = false) const

Converts the value to a bool and returns it.

If type() is not bool, the defaultValue will be returned.

double QJsonValue::toDouble(double defaultValue = 0) const

Converts the value to a double and returns it.

If type() is not Double, the defaultValue will be returned.

QJsonObject QJsonValue::toObject(const QJsonObject & defaultValue) const

Converts the value to an object and returns it.

If type() is not Object, the defaultValue will be returned.

QJsonObject QJsonValue::toObject() const

This is an overloaded function.

Converts the value to an object and returns it.

If type() is not Object, the QJsonObject() will be returned.

QString QJsonValue::toString(const QString & defaultValue = QString()) const

Converts the value to a QString and returns it.

If type() is not String, the defaultValue will be returned.

QVariant QJsonValue::toVariant() const

Converts the value to a QVariant.

The QJsonValue types will be converted as follows:

Constant	Value	Description
QJsonValue::Null	?	QVariant()
QJsonValue::Bool	?	QVariant::Bool(obsolete)
QJsonValue::Double	?	QVariant::Double(obsolete)
QJsonValue::String	?	QVariant::String(obsolete)
QJsonValue::Array	?	QVariantList
QJsonValue::Object	?	QVariantMap
QJsonValue::Undefined	?	QVariant()

See also fromVariant().

Type QJsonValue::type() const

Returns the type of the value.

See also QJsonValue::Type.

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

Returns true if the value is not equal to other.

QJsonValue & QJsonValue::operator=(const QJsonValue & other)

Assigns the value stored in other to this object.