The QVariant class acts like a union for the most common Qt data types. More...

Inheritance diagram for QtCore.QVariant:

Collaboration diagram for QtCore.QVariant:

Public Types
enum	Type { BitArray = 13, Bitmap = 73, Bool = 1, Brush = 66, ByteArray = 12, Char = 7, Color = 67, Cursor = 74, Date = 14, DateTime = 16, Double = 6, EasingCurve = 29, Font = 64, Hash = 28, Icon = 69, Image = 70, Int = 2, Invalid = 0, KeySequence = 76, LastCoreType = 29, LastGuiType = 86, LastType = -1, Line = 23, LineF = 24, List = 9, Locale = 18, LongLong = 4, Map = 8, Matrix = 80, Matrix4x4 = 82, Palette = 68, Pen = 77, Pixmap = 65, Point = 25, PointF = 26, Polygon = 71, Quaternion = 86, Rect = 19, RectF = 20, RegExp = 27, Region = 72, Size = 21, SizeF = 22, SizePolicy = 75, String = 10, StringList = 11, TextFormat = 79, TextLength = 78, Time = 15, Transform = 81, UInt = 3, ULongLong = 5, Url = 17, UserType = 127, Vector2D = 83, Vector3D = 84, Vector4D = 85 }
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Public Member Functions
	QVariant ()


	QVariant (object other)


	QVariant (QDataStream s)


	QVariant (QByteArray bytearray)


	QVariant (QBitArray bitarray)


	QVariant (QLatin1String @string)


	QVariant (QChar qchar)


	QVariant (QDate date)


	QVariant (QTime time)


	QVariant (QDateTime datetime)


	QVariant (QSize size)


	QVariant (QSizeF size)


	QVariant (QPoint pt)


	QVariant (QPointF pt)


	QVariant (QLine line)


	QVariant (QLineF line)


	QVariant (QRect rect)


	QVariant (QRectF rect)


	QVariant (QUrl url)


	QVariant (QLocale locale)


	QVariant (QRegExp regExp)


	QVariant (QEasingCurve easing)


	QVariant (QVariant.Type type)


	QVariant (int i)


	QVariant (uint ui)


	QVariant (long ll)


	QVariant (ulong ull)


	QVariant (bool b)


	QVariant (double d)


	QVariant (float f)


	QVariant (string @string)


	QVariant (Qt.GlobalColor color)


	QVariant (System.Collections.Generic.List< string > stringlist)


	QVariant (System.Collections.Generic.List< System.Object > list)


	QVariant (System.Collections.Generic.Dictionary< System.String, System.Object > map)


virtual void	CreateProxy ()

new bool	CanConvert (QVariant.Type t)


new void	Clear ()


new bool	Convert (QVariant.Type t)


new void	Detach ()

new bool	IsDetached ()

new bool	IsNull ()


new bool	IsValid ()


new void	Load (QDataStream ds)

new void	Save (QDataStream ds)

new void	Swap (object other)


new QBitArray	ToBitArray ()


new bool	ToBool ()


new QByteArray	ToByteArray ()


new QChar	ToChar ()


new QDate	ToDate ()


new QDateTime	ToDateTime ()


new double	ToDouble ()


new double	ToDouble (ref bool ok)


new QEasingCurve	ToEasingCurve ()


new float	ToFloat ()


new float	ToFloat (ref bool ok)


new System.Collections.Generic.Dictionary < System.String, System.Object >	ToHash ()


new int	ToInt ()


new int	ToInt (ref bool ok)


new QLine	ToLine ()


new QLineF	ToLineF ()


new System.Collections.Generic.List < System.Object >	ToList ()


new QLocale	ToLocale ()


new long	ToLongLong ()


new long	ToLongLong (ref bool ok)


new System.Collections.Generic.Dictionary < System.String, System.Object >	ToMap ()


new QPoint	ToPoint ()


new QPointF	ToPointF ()


new double	ToReal ()


new double	ToReal (ref bool ok)


new QRect	ToRect ()


new QRectF	ToRectF ()


new QRegExp	ToRegExp ()


new QSize	ToSize ()


new QSizeF	ToSizeF ()


override string	ToString ()


new System.Collections.Generic.List < string >	ToStringList ()


new QTime	ToTime ()


new uint	ToUInt ()


new uint	ToUInt (ref bool ok)


new ulong	ToULongLong ()


new ulong	ToULongLong (ref bool ok)


new QUrl	ToUrl ()


new QVariant.Type	type ()


new string	TypeName ()


new int	UserType ()


new void	Dispose ()

Static Public Member Functions
static QVariant.Type	NameToType (string name)


static string	TypeToName (QVariant.Type type)

Protected Member Functions
	QVariant (System.Type dummy)

new bool	Cmp (object other)

Protected Attributes
SmokeInvocation	interceptor

Properties
virtual System.IntPtr	SmokeObject `[get, set]`

Detailed Description

The QVariant class acts like a union for the most common Qt data types.

Because C++ forbids unions from including types that have non-default constructors or destructors, most interesting Qt classes cannot be used in unions. Without QVariant, this would be a problem for QObject::property() and for database work, etc.

A QVariant object holds a single value of a single type() at a time. (Some type()s are multi-valued, for example a string list.) You can find out what type, T, the variant holds, convert it to a different type using convert(), get its value using one of the toT() functions (e.g., toSize()) and check whether the type can be converted to a particular type using canConvert().

The methods named toT() (e.g., toInt(), toString()) are const. If you ask for the stored type, they return a copy of the stored object. If you ask for a type that can be generated from the stored type, toT() copies and converts and leaves the object itself unchanged. If you ask for a type that cannot be generated from the stored type, the result depends on the type; see the function documentation for details.

Here is some example code to demonstrate the use of QVariant:

QDataStream out(...);

QVariant v(123); // The 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"); // The variant now contains a QByteArray

v = QVariant(tr("hello")); // The variant now contains a QString

int y = v.toInt(); // y = 0 since v cannot 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", // prints "Type is int"

v.typeName());

v = v.toInt() + 100; // The variant now hold the value 223

v = QVariant(QStringList());

You can even store QList<QVariant> and QMap<QString, QVariant> values in a variant, so you can easily construct arbitrarily complex data structures of arbitrary types. This is very powerful and versatile, but may prove less memory and speed efficient than storing specific types in standard data structures.

QVariant also supports the notion of null values, where you can have a defined type with no value set. However, note that QVariant types can only be cast when they have had a value set.

QVariant x, y(QString()), z(QString(""));

x.convert(QVariant::Int);

// x.isNull() == true

// y.isNull() == true, z.isNull() == false

QVariant can be extended to support other types than those mentioned in the Type enum. See the QMetaType documentation for details.

A Note on GUI Types

Because QVariant is part of the QtCore library, it cannot provide conversion functions to data types defined in QtGui, such as QColor, QImage, and QPixmap. In other words, there is no toColor() function. Instead, you can use the QVariant::value() or the qvariant_cast() template function. For example:

QVariant variant;

...

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

The inverse conversion (e.g., from QColor to QVariant) is automatic for all data types supported by QVariant, including GUI-related types:

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

QVariant variant = color;

Using canConvert() and convert() Consecutively

When using canConvert() and convert() consecutively, it is possible for canConvert() to return true, but convert() to return false. This is typically because canConvert() only reports the general ability of QVariant to convert between types given suitable data; it is still possible to supply data which cannot actually be converted.

For example, canConvert() would return true when called on a variant containing a string because, in principle, QVariant is able to convert strings of numbers to integers. However, if the string contains non-numeric characters, it cannot be converted to an integer, and any attempt to convert it will fail. Hence, it is important to have both functions return true for a successful conversion.

Member Enumeration Documentation

enum QtCore.QVariant.Type

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

Enumerator:

BitArray	A QBitArray
Bitmap	A QBitmap
Bool	A bool
Brush	A QBrush
ByteArray	A QByteArray
Char	A QChar
Color	A QColor
Cursor	A QCursor
Date	A QDate
DateTime	A QDateTime
Double	A double
EasingCurve	A QEasingCurve
Font	A QFont
Hash	A QVariantHash
Icon	A QIcon
Image	A QImage
Int	An int
Invalid	No type
KeySequence	A QKeySequence
LastCoreType
LastGuiType
LastType
Line	A QLine
LineF	A QLineF
List	A QVariantList
Locale	A QLocale
LongLong	A qlonglong
Map	A QVariantMap
Matrix	A QMatrix(obsolete)
Matrix4x4	A QMatrix4x4
Palette	A QPalette
Pen	A QPen
Pixmap	A QPixmap
Point	A QPoint
PointF	A QPointF
Polygon	A QPolygon
Quaternion	A QQuaternion
Rect	A QRect
RectF	A QRectF
RegExp	A QRegExp
Region	A QRegion
Size	A QSize
SizeF	A QSizeF
SizePolicy	A QSizePolicy
String	A QString
StringList	A QStringList
TextFormat	A QTextFormat
TextLength	A QTextLength
Time	A QTime
Transform	A QTransform
UInt	A uint
ULongLong	A qulonglong
Url	A QUrl
UserType	Base value for user-defined types.
Vector2D	A QVector2D
Vector3D	A QVector3D
Vector4D	A QVector4D

Constructor & Destructor Documentation

QtCore.QVariant.QVariant ( System.Type dummy )

protected

QtCore.QVariant.QVariant ( )

Constructs an invalid variant.

QtCore.QVariant.QVariant ( object other )

Constructs a copy of the variant, p, passed as the argument to this constructor.

QtCore.QVariant.QVariant ( QDataStream s )

Reads the variant from the data stream, s.

QtCore.QVariant.QVariant ( QByteArray bytearray )

Constructs a new variant with a bytearray value, val.

QtCore.QVariant.QVariant ( QBitArray bitarray )

Constructs a new variant with a bitarray value, val.

QtCore.QVariant.QVariant ( QLatin1String @ string )

Constructs a new variant with a string value, val.

QtCore.QVariant.QVariant ( QChar qchar )

Constructs a new variant with a char value, c.

QtCore.QVariant.QVariant ( QDate date )

Constructs a new variant with a date value, val.

QtCore.QVariant.QVariant ( QTime time )

Constructs a new variant with a time value, val.

QtCore.QVariant.QVariant ( QDateTime datetime )

Constructs a new variant with a date/time value, val.

QtCore.QVariant.QVariant ( QSize size )

Constructs a new variant with a size value of val.

QtCore.QVariant.QVariant ( QSizeF size )

Constructs a new variant with a size value of val.

QtCore.QVariant.QVariant ( QPoint pt )

Constructs a new variant with a point value of val.

QtCore.QVariant.QVariant ( QPointF pt )

Constructs a new variant with a point value of val.

QtCore.QVariant.QVariant ( QLine line )

Constructs a new variant with a line value of val.

QtCore.QVariant.QVariant ( QLineF line )

Constructs a new variant with a line value of val.

QtCore.QVariant.QVariant ( QRect rect )

Constructs a new variant with a rect value of val.

QtCore.QVariant.QVariant ( QRectF rect )

Constructs a new variant with a rect value of val.

QtCore.QVariant.QVariant ( QUrl url )

Constructs a new variant with a url value of val.

QtCore.QVariant.QVariant ( QLocale locale )

Constructs a new variant with a locale value, l.

QtCore.QVariant.QVariant ( QRegExp regExp )

Constructs a new variant with the regexp value regExp.

QtCore.QVariant.QVariant ( QEasingCurve easing )

Constructs a new variant with an easing curve value, val.

This function was introduced in Qt 4.7.

QtCore.QVariant.QVariant ( QVariant.Type type )

Constructs a null variant of type type.

QtCore.QVariant.QVariant ( int i )

Constructs a new variant with an integer value, val.

QtCore.QVariant.QVariant ( uint ui )

Constructs an invalid variant.

QtCore.QVariant.QVariant ( long ll )

Constructs an invalid variant.

QtCore.QVariant.QVariant ( ulong ull )

Constructs an invalid variant.

QtCore.QVariant.QVariant ( bool b )

Constructs a new variant with a boolean value, val.

QtCore.QVariant.QVariant ( double d )

Constructs a new variant with a floating point value, val.

QtCore.QVariant.QVariant ( float f )

Constructs a new variant with a floating point value, val.

This function was introduced in Qt 4.6.

QtCore.QVariant.QVariant ( string @ string )

Constructs a new variant with a string value, val.

QtCore.QVariant.QVariant ( Qt.GlobalColor color )

Constructs a new variant of type QVariant::Color and initializes it with color.

This is a convenience constructor that allows QVariant(Qt::blue); to create a valid QVariant storing a QColor.

Note: This constructor will assert if the application does not link to the Qt GUI library.

This function was introduced in Qt 4.2.

QtCore.QVariant.QVariant ( System.Collections.Generic.List< string > stringlist )

Constructs a new variant with a string list value, val.

QtCore.QVariant.QVariant ( System.Collections.Generic.List< System.Object > list )

Constructs a new variant with a list value, val.

QtCore.QVariant.QVariant ( System.Collections.Generic.Dictionary< System.String, System.Object > map )

Constructs an invalid variant.

Member Function Documentation

new bool QtCore.QVariant.CanConvert ( QVariant.Type t )

Returns true if the variant's type can be cast to the requested type, t. Such casting is done automatically when calling the toInt(), toBool(), ... methods.

The following casts are done automatically:

TypeAutomatically Cast To

Bool Char, Double, Int, LongLong, String, UInt, ULongLong

ByteArray Double, Int, LongLong, String, UInt, ULongLong

Char Bool, Int, UInt, LongLong, ULongLong

Color String

Date DateTime, String

DateTime Date, String, Time

Double Bool, Int, LongLong, String, UInt, ULongLong

Font String

Int Bool, Char, Double, LongLong, String, UInt, ULongLong

KeySequence Int, String

List StringList (if the list's items can be converted to strings)

LongLong Bool, ByteArray, Char, Double, Int, String, UInt, ULongLong

Point PointF

Rect RectF

String Bool, ByteArray, Char, Color, Date, DateTime, Double, Font, Int, KeySequence, LongLong, StringList, Time, UInt, ULongLong

StringList List, String (if the list contains exactly one item)

Time String

UInt Bool, Char, Double, Int, LongLong, String, ULongLong

ULongLong Bool, Char, Double, Int, LongLong, String, UInt