Stores a single value of almost any data type. More...

Public Types
enum	Type : uint

Public Methods
	QVariant ()

	QVariant (bool value)

	QVariant (const QVariant &other)

	QVariant (double value)

	QVariant (float value)

	QVariant (int value)

	QVariant (QBitArray value)

	QVariant (QByteArray value)

	QVariant (QChar32 value)

	QVariant (QDataStream &stream)

	QVariant (QDate value)

	QVariant (QDateTime value)

	QVariant (QEasingCurve value)

	QVariant (QHash< QString, QVariant > value)

	QVariant (qint64 value)

	QVariant (QJsonArray value)

	QVariant (QJsonDocument value)

	QVariant (QJsonObject value)

	QVariant (QJsonValue value)

	QVariant (QLine value)

	QVariant (QLineF value)

	QVariant (QList< QVariant > value)

	QVariant (QLocale value)

	QVariant (QMap< QString, QVariant > value)

	QVariant (QModelIndex value)

	QVariant (QMultiHash< QString, QVariant > value)

	QVariant (QMultiMap< QString, QVariant > value)

	QVariant (QPersistentModelIndex value)

	QVariant (QPoint value)

	QVariant (QPointF value)

	QVariant (QRect value)

	QVariant (QRectF value)

	QVariant (QRegularExpression8 value)

	QVariant (QSize value)

	QVariant (QSizeF value)

	QVariant (QString value)

	QVariant (QString16 value)

	QVariant (QStringList value)

	QVariant (QTime value)

	QVariant (quint64 value)

	QVariant (QUrl value)

	QVariant (QUuid value)

	QVariant (QVariant &&other) = default

	QVariant (Type type)

	QVariant (uint typeId, const void *copy)

	QVariant (uint value)

	~QVariant () = default

template<typename T >
bool	canConvert () const

bool	canConvert (uint newType) const

void	clear ()

template<typename T >
bool	convert ()

bool	convert (uint newType)

int64_t	enumToInt () const

uint64_t	enumToUInt () const

template<typename T >
T	getData () const

template<typename T >
std::optional< T >	getDataOr () const

bool	isEnum () const

bool	isValid () const

std::optional< QVariant >	maybeConvert (uint requested_type) const

bool	operator!= (const QVariant &other) const

QVariant &	operator= (const QVariant &other)

QVariant &	operator= (QVariant &&other)

bool	operator== (const QVariant &other) const

void	setValue (const QVariant &value)

template<typename T >
void	setValue (const T &value)

void	swap (QVariant &other)

QBitArray	toBitArray () const

bool	toBool (bool *ok=nullptr) const

QByteArray	toByteArray () const

QChar32	toChar () const

QDate	toDate () const

QDateTime	toDateTime () const

double	toDouble (bool *ok=nullptr) const

QEasingCurve	toEasingCurve () const

float	toFloat (bool *ok=nullptr) const

QHash< QString, QVariant >	toHash () const

int	toInt (bool *ok=nullptr) const

QJsonArray	toJsonArray () const

QJsonDocument	toJsonDocument () const

QJsonObject	toJsonObject () const

QJsonValue	toJsonValue () const

QLine	toLine () const

QLineF	toLineF () const

QList< QVariant >	toList () const

QLocale	toLocale () const

qint64	toLongLong (bool *ok=nullptr) const

QMap< QString, QVariant >	toMap () const

QModelIndex	toModelIndex () const

QMultiHash< QString, QVariant >	toMultiHash () const

QMultiMap< QString, QVariant >	toMultiMap () const

QPersistentModelIndex	toPersistentModelIndex () const

QPoint	toPoint () const

QPointF	toPointF () const

qreal	toReal (bool *ok=nullptr) const

QRect	toRect () const

QRectF	toRectF () const

QRegularExpression8	toRegularExpression () const

QSize	toSize () const

QSizeF	toSizeF () const

QString8	toString () const

QString16	toString16 () const

QStringList	toStringList () const

QTime	toTime () const

uint	toUInt (bool *ok=nullptr) const

quint64	toULongLong (bool *ok=nullptr) const

QUrl	toUrl () const

QUuid	toUuid () const

Type	type () const

QString	typeName () const

uint	userType () const

template<typename Requested >
Requested	value () const

Static Public Methods
static QVariant	fromValue (const QVariant &value)

template<typename T >
static QVariant	fromValue (const T &value)

static uint	nameToType (const QString &name)

static QString	typeToName (uint typeId)

template<typename T >
static uint	typeToTypeId ()

Related Functions
These are not member functions
#define	CS_DECLARE_METATYPE(TYPE)

bool	operator!= (const QVariant &v1, const QVariant &v2)

QDataStream &	operator<< (QDataStream &stream, QVariant &data)

bool	operator== (const QVariant &v1, const QVariant &v2)

QDataStream &	operator>> (QDataStream &stream, const QVariant &data)

T	qvariant_cast (const QVariant &x)

	QVariantHash

	QVariantList

	QVariantMap

Detailed Description

The QVariant class is used to store a single value of some other data type. Not every value can be stored in a QVariant using every data type. For example, a QString can be retrieved as QKeySequence but it can not be retrieved as a QPoint. The QObject::property() system relies on the enums, methods, and data storage which is provided by this class.

The data stored in a QVariant has a corresponding integer type id which is defined in the QVariant::Type enum. If there is no match then the integer type id is represented by the value QVariant::Type::UserType.

The QVariant::Type enum contains a list of the CsCore and CsGui data types most often associated with variants. QVariant can be extended to support other data types by calling the CS_DECLARE_METATYPE() macro.

An important feature of the property system is the ability to provide a string representation for a given data type. For example, given the data type QStringList the string representation would be "QStringList" and for a bool the string representation would be "bool". To retrieve this string call typeName() on an existing QVariant object.

To find the integer type id which corresponds to a given data type name use the method nameToType().

Containers

There are five QVariant types which can be used to represent a container of QVariants. This allows storing complex data structures of arbitrary types. Although this is a useful feature and very convenient, it may be less efficient than storing the data in a standard strongly typed container.

The "to" Methods

There are a variety of methods which begin with the name "to" and are used to convert a variant value to the requested type. For example toString(), toDate(), or toInt() are methods to convert the variant to a QString, QDate, and an integer respectively. The returned value will be a copy even if no conversion occurs. If the conversion fails the return value will be an empty, null, or zero based on the requested type.

The following example shows several ways to use a QVariant.

QDataStream out(...);
 
QVariant v(123);                      // variant now contains an int
int x = v.toInt();                    // x = 123
out << v;                             // writes a type tag and an int to out
 
v = QVariant("hello");                // variant now contains a QByteArray
v = QVariant(tr("hello"));            // variant now contains a QString
 
int y = v.toInt();                    // y = 0 since v can not be converted to an int
 
QString s = v.toString();             // s = tr("hello")  (see QObject::tr())
out << v;                             // Writes a type tag and a QString to out
 
QDataStream in(...);                  // (opening the previously written stream)
in >> v;                              // reads an Int variant
int z = v.toInt();                    // z = 123
 
qDebug("Type is %s", v.typeName());   // prints "Type is int"
 
v = v.toInt() + 100;                  // variant now holds the value 223
v = QVariant(QStringList());

GUI Usage

QVariant is part of the CsCore library and can not provide conversion functions to data types defined in another library such as CsGui. This means you will not find a toColor() method to convert a QVariant value to a QColor.

The correct way to accomplish this is by using the templated value() method.

QVariant data;

QColor color = data.value<QColor>();

Converting from a QColor to a QVariant is automatic for data types which are supported by QVariant.

QColor color = palette().background().color();

QVariant data = color;

Using canConvert() and convert()

To find out what data type the QVariant holds use the type() method and to convert the object to a different type use convert().

To verify if a given object can be converted to a different type, use canConvert(). It is possible for canConvert() to return true, but then convert() will return false. This happens because canConvert() only looks at the source and target data types, not the actual values.

For example, canConvert(Type::Int) will return true when called on a variant which contains a string. Passing this enum asks if the string can be converted to an int, which is valid. However, if the string contains non-numeric characters it can not be converted to an integer, so convert() will fail.

Member Enumeration Documentation

enum QVariant::Type : uint

This enum type defines the types of variable that a QVariant can contain.

Constant	Description
`QVariant::Invalid`	Invalid data type
`QVariant::BitArray`	QBitArray
`QVariant::Bitmap`	QBitmap
`QVariant::Bool`	bool
`QVariant::Brush`	QBrush
`QVariant::ByteArray`	QByteArray
`QVariant::Char`	QChar
`QVariant::Char32`	QChar32
`QVariant::Color`	QColor
`QVariant::Cursor`	QCursor
`QVariant::Date`	QDate
`QVariant::DateTime`	QDateTime
`QVariant::Double`	double
`QVariant::EasingCurve`	QEasingCurve
`QVariant::Font`	QFont
`QVariant::Hash`	QVariantHash
`QVariant::Icon`	QIcon
`QVariant::Image`	QImage
`QVariant::Int`	int
`QVariant::KeySequence`	QKeySequence
`QVariant::Line`	QLine
`QVariant::LineF`	QLineF
`QVariant::List`	QVariantList
`QVariant::Locale`	QLocale
`QVariant::LongLong`	long long
`QVariant::Map`	QVariantMap
`QVariant::Matrix`	QMatrix
`QVariant::Transform`	QTransform
`QVariant::Matrix4x4`	QMatrix4x4
`QVariant::Palette`	QPalette
`QVariant::Pen`	QPen
`QVariant::Pixmap`	QPixmap
`QVariant::Point`	QPoint
`QVariant::PointF`	QPointF
`QVariant::Polygon`	QPolygon
`QVariant::Quaternion`	QQuaternion
`QVariant::Rect`	QRect
`QVariant::RectF`	QRectF
`QVariant::RegularExpression`	QRegularExpression
`QVariant::Region`	QRegion
`QVariant::Size`	QSize
`QVariant::SizeF`	QSizeF
`QVariant::SizePolicy`	QSizePolicy
`QVariant::String`	QString
`QVariant::String8`	QString8
`QVariant::String16`	QString16
`QVariant::StringList`	QStringList
`QVariant::TextFormat`	QTextFormat
`QVariant::TextLength`	QTextLength
`QVariant::Time`	QTime
`QVariant::UInt`	uint
`QVariant::ULongLong`	quint64
`QVariant::Url`	QUrl
`QVariant::Vector2D`</td	QVector2D
`QVariant::Vector3D`	QVector3D
`QVariant::Vector4D`	QVector4D
`QVariant::UserType`	Base value for user defined types

Constructor & Destructor Documentation

QVariant::QVariant ( )

inline

Constructs an empty QVariant.

QVariant::QVariant ( Type type )

Constructs a empty variant with the data type of type.

QVariant::QVariant	(	uint	typeId,
		const void *	copy
	)

Constructs a variant with of a type of typeId and initializes with copy, if the copy is not a null pointer. Ensure you pass the address of the variable you want stored.

This constructor in seldom used. The QVariant::fromValue() method should be used instead to construct variants from the pointer types represented by VoidStar, QObjectStar and QWidgetStar.

See also: QVariant::fromValue(), Type

QVariant::QVariant ( const QVariant & other )

Copy constructs a new QVariant from other.

QVariant::QVariant ( QVariant && other )

default

Move constructs a new QVariant from other.

QVariant::QVariant ( bool value )

Constructs a new variant with a boolean of value.

QVariant::QVariant ( int value )

Constructs a new variant with an integer of value.

QVariant::QVariant ( uint value )

Constructs a new variant with an unsigned integer of value.

QVariant::QVariant ( qint64 value )

Constructs a new variant with a qint64 integer of value.

QVariant::QVariant ( quint64 value )

Constructs a new variant with a quint64 integer of value.

QVariant::QVariant ( double value )

Constructs a new variant with a floating point of value.

QVariant::QVariant ( float value )

Constructs a new variant with a floating point of value.

QVariant::QVariant ( QChar32 value )

Constructs a new variant with a QChar of value.

QVariant::QVariant ( QString value )

Constructs a new variant with a QString of value.

QVariant::QVariant ( QByteArray value )

Constructs a new variant with a QByteArray of value.

QVariant::QVariant ( QBitArray value )

Constructs a new variant with a QBitArray of value.

QVariant::QVariant ( QString16 value )

Constructs a new variant with a QString16 of value.

QVariant::QVariant ( QStringList value )

Constructs a new variant with a QStringList of value.

QVariant::QVariant ( QRegularExpression8 value )

Constructs a new variant with a QRegularExpression of value.

QVariant::QVariant ( QDate value )

Constructs a new variant with a QDate of value.

QVariant::QVariant ( QTime value )

Constructs a new variant with a QTime of value.

QVariant::QVariant ( QDateTime value )

Constructs a new variant with a QDateTime of value.

QVariant::QVariant ( QLocale value )

Constructs a new variant with a QLocale of value.

QVariant::QVariant ( QList< QVariant > value )

Constructs a new variant with a list of QVariants contained of value.

QVariant::QVariant ( QHash< QString, QVariant > value )

Constructs a new variant with a hash of QVariants contained of value.

QVariant::QVariant ( QMap< QString, QVariant > value )

Constructs a new variant with a map of QVariants contained of value.

QVariant::QVariant ( QMultiHash< QString, QVariant > value )

Constructs a new variant with a multi hash of value.

QVariant::QVariant ( QMultiMap< QString, QVariant > value )

Constructs a new variant with a multi map of value.

QVariant::QVariant ( QJsonValue value )

Constructs a new variant with a QJsonValue of value.

QVariant::QVariant ( QJsonObject value )

Constructs a new variant with a QJsonObject of value.

QVariant::QVariant ( QJsonArray value )

Constructs a new variant with a QJsonArray of value.

QVariant::QVariant ( QJsonDocument value )

Constructs a new variant with a QJsonDocument of value.

QVariant::QVariant ( QRect value )

Constructs a new variant with a QRect of value.

QVariant::QVariant ( QRectF value )

Constructs a new variant with a QRectF of value.

QVariant::QVariant ( QSize value )

Constructs a new variant with a QSize of value.

QVariant::QVariant ( QSizeF value )

Constructs a new variant with a QSizeF of value.

QVariant::QVariant ( QLine value )

Constructs a new variant with a QLine of value.

QVariant::QVariant ( QLineF value )

Constructs a new variant with a QLineF of value.

QVariant::QVariant ( QPoint value )

Constructs a new variant with a QPoint of value.

QVariant::QVariant ( QPointF value )

Constructs a new variant with a QPointF of value.

QVariant::QVariant ( QEasingCurve value )

Constructs a new variant with an QEasingCurve of value.

QVariant::QVariant ( QModelIndex value )

Constructs a new variant with a QModelIndex of value.

QVariant::QVariant ( QPersistentModelIndex value )

Constructs a new variant with a QPersistentModelIndex of value.

QVariant::QVariant ( QUuid value )

Constructs a new variant with a QUuid of value.

QVariant::QVariant ( QUrl value )

Constructs a new variant with a QUrl of value.

QVariant::QVariant ( QDataStream & stream )

Reads the variant from the data given stream.

QVariant::~QVariant ( )

default

Destroys the QVariant and the contained object.

Method Documentation

template<typename T >

bool QVariant::canConvert ( ) const

inline

Returns true if the variant can be converted to the template type T, otherwise false.

QVariant v = 42;
 
v.canConvert<int>();              // returns true
v.canConvert<QString>();          // returns true
 
MyCustomStruct s;
v.setValue(s);
 
v.canConvert<int>();              // returns false
v.canConvert<MyCustomStruct>();   // returns true

See also: convert()

bool QVariant::canConvert ( uint newType ) const

Returns true if the current variant type can be cast to the requested variant newType. It is possible for this method to return true, but then convert() will return false. This happens because this method only looks at the source and target data types, not the actual values.

Current Type	Requested Type
Bitmap	Image, Pixmap
Bool	ByteArray, Char, Double, Float, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong, UShort
Brush	Color, Pixmap
ByteArray	Bool, Char, Color, Double, Float, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong, UShort
Char	Bool, ByteArray, Int, Long, LongLong, QChar, Short, SChar, UChar, UInt, ULong, ULongLong, UShort
QChar	Bool, ByteArray, Char, Int, Long, LongLong, Short, SChar, String, String16, UChar, UInt, LongLong, ULong, ULongLong, UShort
SChar	Bool, ByteArray, Char, Int, Long, LongLong, QChar, Short, UChar, UInt, ULong, ULongLong, UShort
UChars	Bool, ByteArray, Char, Int, Long, LongLong, QChar, SChar, Short, UInt, ULong, ULongLong, UShort
Color	Brush, ByteArray, String, String16
Date	DateTime, String, String16
DateTime	Date, String, String16, Time
Double	Bool, ByteArray, Char, Float, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong, UShort
Float	Bool, ByteArray, Char, Double, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong, UShort
Font	String, String16
Image	Bitmap, Pixmap
Hash	Map
Int	Bool, ByteArray, Char, Double, Float, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong, UShort
JsonArray	List
JsonObject	Hash, Map
JsonValue	Bool, Char, Double, Float, Hash, Int, Long, LongLong, List, Map, QChar, Short, SChar, String, String16, UChar, UInt, ULong, ULongLong, UShort
KeySequence	String, String16
Line	LineF
LineF	Line
List	StringList Note: Conversion is only valid when the items in the List can be converted to Strings
Long	Bool, ByteArray, Char, Double, Float, Int, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong, UShort
LongLong	Bool, ByteArray, Char, Double, Float, Int, Long, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong, UShort
Map	Hash
ModelIndex	PersistentModelIndex
PersistentModelIndex	ModelIndex
Pixmap	Bitmap, Brush, Image
Point	PointF
PointF	Point
Rect	RectF
RectF	Rect
Short	Bool, ByteArray, Char, Double, Float, Int, Long, LongLong, QChar, SChar, String, String16, UChar, UInt, ULong, ULongLong, UShort
Size	SizeF
SizeF	Size
String, String16	Bool, ByteArray, Char, Color, Date, DateTime, Double, Float, Font, Int, KeySequence, Long, LongLong, QChar, SChar, Short, StringList, Time, UChar, UInt, ULong, ULongLong, Url, UShort, Uuid
StringList	List, String, String16 Note: Conversions to Strings are only valid when the StringList contains exactly one item
Time	String, String16
UInt	Bool, ByteArray, Char, Double, Float, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, ULong, ULongLong, UShort
ULong	Bool, ByteArray, Char, Double, Float, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULongLong, UShort
ULongLong	Bool, ByteArray, Char, Double, Float, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, UShort
UShort	Bool, ByteArray, Char, Double, Float, Int, Long, LongLong, QChar, SChar, Short, String, String16, UChar, UInt, ULong, ULongLong
Url	ByteArray, String, String16
Uuid	ByteArray, String, String16

See also: convert()

void QVariant::clear ( )

Sets this variant to an invalid data type and the integer type id to zero, which is the enum value QVariant::Invalid.

template<typename T >

bool QVariant::convert ( )

inline

Casts the variant to the requested type T. If the conversion can not be done the variant is set to an invalid data type and the enum type is set to QVariant::Invalid.

Returns true if the variant was successfully converted, otherwise returns false.

See also: canConvert(), clear()

bool QVariant::convert ( uint newType )

Casts the variant to the requested type newType. If the conversion can not be done the variant is set to an invalid data type and the enum type is set to QVariant::Invalid.

Returns true if the variant was successfully converted, otherwise returns false.

See also: canConvert(), clear()

int64_t QVariant::enumToInt ( ) const

If the current QVariant contains a value which is an enum or a flag this method will return the value as a signed integer. Otherwise returns the value 0.

uint64_t QVariant::enumToUInt ( ) const

If the current QVariant contains a value which is an enum or a flag this method will return the value as an unsigned integer. Otherwise returns the value 0.

QVariant QVariant::fromValue ( const QVariant & value )

inlinestatic

Returns a QVariant containing a copy of value. This is the same as calling setValue() on a new QVariant.

See also: setValue(), value()

template<typename T >

QVariant QVariant::fromValue ( const T & value )

inlinestatic

Returns a QVariant containing a copy of value. This is the same as calling setValue() on a new QVariant.

MyCustomStruct s;

return QVariant::fromValue(s);

Note: If you are working with custom types use the CS_DECLARE_METATYPE() macro to register the custom type.

See also: setValue(), value()

template<typename T >

T QVariant::getData ( ) const

Returns the value for this QVariant if the data type of the QVariant matches T. Otherwise returns a default constructed T.

See also: getDataOr()

template<typename T >

std::optional< T > QVariant::getDataOr ( ) const

Returns the value in this QVariant if the type is T. Otherwise this method returns an empty std::optional of type T.

Note: Using the return type of std::optional provides a clean way to indicate the requested data type T was not stored in this variant. A caller of this method can test the optional by calling has_value().

QVariant var = someMethod();
std::optional<QString> result = var.getDataOr<QString>();
 
if (result.has_value()) {
   return result.value().toLower();
 
} else {
   return QString("Variant did not contain a string");
}

See also: getData()

bool QVariant::isEnum ( ) const

Returns true if the current QVariant contains a value which is an enum or a flag.

bool QVariant::isValid ( ) const

inline

Returns true if the data type in this variant is not QVariant::Invalid, otherwise returns false.

std::optional< QVariant > QVariant::maybeConvert ( uint requested_type ) const

Returns an std::optional containing the value of this QVariant converted to the requested_type or an empty optional if the conversion fails.

Note: Using the return type of std::optional provides a clean way to indicate the requested data type T was not stored in this variant. A caller of this method can test the optional by calling has_value().

uint QVariant::nameToType ( const QString & name )

static

Converts the data type specified by name, to the corresponding integer type id. If the name can not be converted the return value is zero.

See also: typeToName()

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

inline

Compares this QVariant with other and returns true if they are not equal, otherwise returns false.

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

Copy assigns from other and returns a reference to this object.

QVariant & QVariant::operator= ( QVariant && other )

inline

Move assigns from other and returns a reference to this object.

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

inline

Compares this QVariant with other and returns true if they are equal, otherwise returns false. In the case of custom types, their equality operators are not called. Instead their addresses are compared.

void QVariant::setValue ( const QVariant & value )

inline

Copies the data in value into this QVariant.

See also: value(), fromValue(), canConvert()

template<typename T >

void QVariant::setValue ( const T & value )

Copies value into this QVariant.

QVariant v;
 
v.setValue(5);
int i = v.toInt();         // i is now 5
QString s = v.toString()   // s is now "5"
 
MyCustomStruct c;
v.setValue(c);
 
MyCustomStruct c2 = v.value<MyCustomStruct>();

See also: value(), fromValue(), canConvert()

void QVariant::swap ( QVariant & other )

inline

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

QBitArray QVariant::toBitArray ( ) const

Returns the variant as a QBitArray if the variant has a data type of BitArray, otherwise returns an empty QBitArray.

See also: canConvert(), convert()

bool QVariant::toBool ( bool * ok = nullptr ) const

Returns the variant as a bool if the variant has a data type of Bool.

Returns true if the variant has a data type of Bool, Char, Double, Int, LongLong, UInt, or ULongLong and the value is non-zero, or if the variant has type String or ByteArray and its lower case content is not empty, "0" or "false", otherwise returns false.

See also: canConvert(), convert()

QByteArray QVariant::toByteArray ( ) const

Returns the variant as a QByteArray if the variant has a data type of ByteArray or String, otherwise returns an empty byte array.

See also: canConvert(), convert()

QChar32 QVariant::toChar ( ) const

Returns the variant as a QChar32 if the variant has a data type of QChar, Char, Int, or UInt. If the conversion fails it returns a null QChar32.

See also: canConvert(), convert()

QDate QVariant::toDate ( ) const

Returns the variant as a QDate if the variant has a data type of Date, DateTime, or String, otherwise returns an invalid date. If the type() is String, an invalid date will be returned if the string can not be parsed as a Qt::ISODate format date.

See also: canConvert(), convert()

QDateTime QVariant::toDateTime ( ) const

Returns the variant as a QDateTime if the variant has a data type of DateTime, Date, or String, otherwise returns an invalid date/time.

If the type() is String, an invalid date/time will be returned if the string can not be parsed as a Qt::ISODate format date/time.

See also: canConvert(), convert()

double QVariant::toDouble ( bool * ok = nullptr ) const

Returns the variant as a double if the variant has a data type of Double, Float, Bool, ByteArray, Int, LongLong, String, UInt, or ULongLong, otherwise returns 0.0. If ok is not a nullptr, this method will set the value according to the success of the conversion. The value is false to indicate the conversion failed, otherwise ok is set to true.

See also: canConvert(), convert()

QEasingCurve QVariant::toEasingCurve ( ) const

Returns the variant as a QEasingCurve if the variant has a data type of EasingCurve, otherwise returns a default easing curve.

See also: canConvert(), convert()

float QVariant::toFloat ( bool * ok = nullptr ) const

Returns the variant as a float if the variant has a data type of Double, Float, Bool, ByteArray, Int, LongLong, String, UInt, or ULongLong, otherwise returns 0.0. If ok is not a nullptr, this method will set the value according to the success of the conversion. The value is false to indicate the conversion failed, otherwise ok is set to true.

See also: canConvert(), convert()

QHash< QString, QVariant > QVariant::toHash ( ) const

Returns the variant as a QHash<QString, QVariant> if the variant has a data type of Hash, otherwise returns an empty QHash.

See also: canConvert(), convert()

int QVariant::toInt ( bool * ok = nullptr ) const

Returns the variant as an int if the variant has a data type of Int, Bool, ByteArray, Char, Double, LongLong, String, UInt, or ULongLong, otherwise return a value of 0. If ok is not a nullptr, this method will set the value according to the success of the conversion. The value is false to indicate the conversion failed, otherwise ok is set to true.

Warning: If the value is convertible to a LongLong but is too large to be represented in an int, the resulting arithmetic overflow will not be reflected in ok. A simple workaround is to use QString8::toInteger().

See also: canConvert(), convert()

QJsonArray QVariant::toJsonArray ( ) const

Returns the variant as a QJsonArray if the variant has a data type of JsonArray, otherwise returns a default constructed QJsonArray.

See also: canConvert(), convert()

QJsonDocument QVariant::toJsonDocument ( ) const

Returns the variant as a QJsonDocument if the variant has a data type of JsonDocument, otherwise returns a default constructed QJsonDocument.

See also: canConvert(), convert()

QJsonObject QVariant::toJsonObject ( ) const

Returns the variant as a QJsonObject if the variant has a data type of JsonObject, otherwise returns a default constructed QJsonObject.

See also: canConvert(), convert()

QJsonValue QVariant::toJsonValue ( ) const

Returns the variant as a QJsonValue if the variant has a data type of JsonValue, otherwise returns a default constructed QJsonValue.

See also: canConvert(), convert()

QLine QVariant::toLine ( ) const

Returns the variant as a QLine if the variant has a data type of Line, otherwise returns an invalid QLine.

See also: canConvert(), convert()

QLineF QVariant::toLineF ( ) const

Returns the variant as a QLineF if the variant has a data type of LineF, otherwise returns an invalid QLineF.

See also: canConvert(), convert()

QList< QVariant > QVariant::toList ( ) const

Returns the variant as a QVariantList if the variant has a data type of List or StringList, otherwise returns an empty list.

See also: canConvert(), convert()

QLocale QVariant::toLocale ( ) const

Returns the variant as a QLocale if the variant has a data type of Locale, otherwise returns an invalid QLocale.

See also: canConvert(), convert()

qint64 QVariant::toLongLong ( bool * ok = nullptr ) const

Returns the variant as a qint64 integer if the variant has a data type of LongLong, Bool, ByteArray, Char, Double, Int, String, UInt, or ULongLong, otherwise returns 0. If ok is not a nullptr, this method will set the value according to the success of the conversion. The value is false to indicate the conversion failed, otherwise ok is set to true.

See also: canConvert(), convert()

QMap< QString, QVariant > QVariant::toMap ( ) const

Returns the variant as a QMap<QString, QVariant> if the variant has a data type of Map, otherwise returns an empty QMap.

See also: canConvert(), convert()

QModelIndex QVariant::toModelIndex ( ) const

Returns the variant as a QModelIndex if the variant has a data type of ModelIndex, otherwise returns a default constructed QModelIndex.

See also: canConvert(), convert()

QMultiHash< QString, QVariant > QVariant::toMultiHash ( ) const

Returns the variant as a QMultiHash<QString, QVariant> if the variant has a data type of MultiHash, otherwise returns an empty multi QMultiHash.

See also: canConvert(), convert()

QMultiMap< QString, QVariant > QVariant::toMultiMap ( ) const

Returns the variant as a QMultiMap<QString, QVariant> if the variant has a data type of MultiMap, otherwise returns an empty multi QMultiMap.

See also: canConvert(), convert()

QPersistentModelIndex QVariant::toPersistentModelIndex ( ) const

Returns the variant as a QPersistentModelIndex if the variant has a data type of PersistentModelIndex, otherwise returns a default constructed QPersistentModelIndex.

See also: canConvert(), convert(), toPersistentModelIndex()

QPoint QVariant::toPoint ( ) const

Returns the variant as a QPoint if the variant has a data type of Point or PointF, otherwise returns a null QPoint.

See also: canConvert(), convert()

QPointF QVariant::toPointF ( ) const

Returns the variant as a QPointF if the variant has a data type of Point or PointF, otherwise returns a null QPointF.

See also: canConvert(), convert()

qreal QVariant::toReal ( bool * ok = nullptr ) const

Returns the variant as a qreal if the variant has a data type of Double, Float, Bool, ByteArray, Int, LongLong, String, UInt, or ULongLong, otherwise returns 0.0. If ok is not a nullptr, this method will set the value according to the success of the conversion. The value is false to indicate the conversion failed, otherwise ok is set to true.

See also: canConvert(), convert()

QRect QVariant::toRect ( ) const

Returns the variant as a QRect if the variant has a data type of Rect, otherwise returns an invalid QRect.

See also: canConvert(), convert()

QRectF QVariant::toRectF ( ) const

Returns the variant as a QRectF if the variant has a data type of Rect or RectF, otherwise returns an invalid QRectF.

See also: canConvert(), convert()

QRegularExpression8 QVariant::toRegularExpression ( ) const

Returns the variant as a QRegularExpression8 if the variant has a data type of RegularExpression otherwise returns an empty QRegularExpression8.

See also: canConvert(), convert()

QSize QVariant::toSize ( ) const

Returns the variant as a QSize if the variant has a data type of Size, otherwise returns an invalid QSize.

See also: canConvert(), convert()

QSizeF QVariant::toSizeF ( ) const

Returns the variant as a QSizeF if the variant has a data type of SizeF, otherwise returns an invalid QSizeF.

See also: canConvert(), convert()

QString8 QVariant::toString ( ) const

Returns the variant as a QString8 if the variant has a data type of String, Bool, ByteArray, Char, QDate, DateTime, Double, Int, LongLong, StringList, Time, UInt, or ULongLong, otherwise returns an empty string.

See also: canConvert(), convert()

QString16 QVariant::toString16 ( ) const

Returns the variant as a QString16 if the variant has a data type of String, Bool, ByteArray, Char, Date, DateTime, Double, Int, LongLong, QStringList, Time, UInt, or ULongLong, otherwise returns an empty string.

See also: canConvert(), convert()

QStringList QVariant::toStringList ( ) const

Returns the variant as a QStringList if the variant has a data type of StringList, String, or List of a type that can be converted to QString, otherwise returns an empty list.

See also: canConvert(), convert()

QTime QVariant::toTime ( ) const

Returns the variant as a QTime if the variant has a data type of Time, DateTime, or String, otherwise returns an invalid time. If the type() is QString, an invalid time will be returned if the string can not be parsed as a Qt::ISODate format time.

See also: canConvert(), convert()

uint QVariant::toUInt ( bool * ok = nullptr ) const

Returns the variant as an unsigned integer if the variant has a data type of UInt, Bool, ByteArray, Char, Double, Int, LongLong, String, or ULongLong, otherwise returns 0. If ok is not a nullptr, this method will set the value according to the success of the conversion. The value is false to indicate the conversion failed, otherwise ok is set to true.

Warning: If the value is convertible to a ULongLong but is too large to be represented in an unsigned int, the resulting arithmetic overflow will not be reflected in ok. A simple workaround is to use QString::toUInt().

See also: canConvert(), convert()

quint64 QVariant::toULongLong ( bool * ok = nullptr ) const

Returns the variant as an quint64 integer if the variant has a data type of ULongLong, Bool, ByteArray, Char, Double, Int, LongLong, String, or UInt, otherwise returns 0. If ok is not a nullptr, this method will set the value according to the success of the conversion. The value is false to indicate the conversion failed, otherwise ok is set to true.

See also: canConvert(), convert()

QUrl QVariant::toUrl ( ) const

Returns the variant as a QUrl if the variant has a data type of Url, otherwise returns an invalid QUrl.

See also: canConvert(), convert()

QUuid QVariant::toUuid ( ) const

Returns the variant as a QUuid if the variant has a data type of Uuid or String, otherwise returns a default constructed QUuid.

See also: canConvert(), convert()

Type QVariant::type ( ) const

Returns the enum value corresponding to the data type which is currently stored in this variant. Returns QVariant::UserType if the data type is not one of the pre-defined types.

See also: userType()

QString QVariant::typeName ( ) const

Returns the name of the data type or class stored in the variant. For example, for the class QFont this method will return "QFont". For primitive types like bool this method will return "bool". If the variant is empty returns an empty string.

For user defined data types this method will return the name which was previously registered when CS_DECLARE_METATYPE() was called.

QString QVariant::typeToName ( uint typeId )

static

Converts the given integer type id typeId to the name of the corresponding data type. If the typeId is QVariant::Invalid this method returns an empty string.

See also: nameToType()

template<typename T >

uint QVariant::typeToTypeId ( )

inlinestatic

Returns the integer type id corresponding to the template parameter T.

uint QVariant::userType ( ) const

Returns the integer type id for this variant. For non-user defined values, which are listed in the QVariant::Type enum, this method returns the same result as calling the type() method.

See also: type()

template<typename Requested >

Requested QVariant::value ( ) const

Returns the value in this variant if it can be converted to the data type specified in the template parameter Requested.

Calling canConvert() will indicate whether the current type can be converted to a particular Requested type. If the value can not be converted, a default constructed value of type Requested will be returned.

QVariant data = 42;
 
// example 1
int cnt = data.value<int>();                  // same as calling data.toInt()
 
// example 2
QString str = data.value<QString>();          // same as calling data.toString(), str is now "42"
 
// example 3
// conConvert() will return false since 42 can not be converted to MyCustomStruct
 
MyCustomStruct structA;
 
if (data.canConvert<MyCustomStruct>()) {
   structA = data.value<MyCustomStruct>();
}
 
// example 4
// following call to value() will fail, structB will contain a default constructed value
 
MyCustomStruct structB = data.value<MyCustomStruct>();

See also: setValue(), fromValue(), canConvert()

Friends And Related Function Documentation

#define CS_DECLARE_METATYPE

This macro makes the Type known to the Variant system. The Type being registered must have a public default constructor, a public copy constructor and a public destructor. It is recommended the Type should have and support an operator==() method.

This macro should be placed after the declaration of the class or struct, which is usually in the header file.

The following is an example of a typical use case.

class MyNewClass {
   int i;
};
 
CS_DECLARE_METATYPE(MyNewClass)

If MyNewClass is located within a namespace the CS_DECLARE_METATYPE() macro needs to appear outside the namespace.

namespace MyProject {
   // ...
}
 
CS_DECLARE_METATYPE(MyProject::MyNewClass)

The following is an example of how to use MyNewClass in a QVariant.

MyNewClass obj;
 
QVariant data;
data.setValue(obj);         // copy obj into a variant
 
// ...
 
// retrieve the value
MyNewClass newObj = data.value<MyNewClass>();

bool operator!=	(	const QVariant &	v1,
		const QVariant &	v2
	)

QDataStream & operator<<	(	QDataStream &	stream,
		QVariant &	data
	)

See also: operator>>()

bool operator==	(	const QVariant &	v1,
		const QVariant &	v2
	)

QDataStream & operator>>	(	QDataStream &	stream,
		const QVariant &	data
	)

See also: operator<<()

T qvariant_cast< T > ( const QVariant & x )

Deprecated:: Use x.value<T>() instead.

See also: QVariant::value()

QVariantHash ( )

QVariantList ( )

QVariantMap ( )

Public Types

Public Methods

Static Public Methods

Related Functions

Detailed Description

Containers

The "to" Methods

GUI Usage

Using canConvert() and convert()

Member Enumeration Documentation

Constructor & Destructor Documentation

Method Documentation

Friends And Related Function Documentation