The QVariant class acts like a union for the most common Qt data types. More...
| Header: | #include <QVariant> |
| CMake: | find_package(Qt6 COMPONENTS Core REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Core) |
| qmake: | QT += core |
| QVariant(QVariant &&other) | |
| QVariant(const QPersistentModelIndex &val) | |
| QVariant(const QModelIndex &val) | |
| QVariant(const QJsonDocument &val) | |
| QVariant(const QJsonArray &val) | |
| QVariant(const QJsonObject &val) | |
| QVariant(const QJsonValue &val) | |
| QVariant(const QUrl &val) | |
| QVariant(const QUuid &val) | |
| QVariant(const QEasingCurve &val) | |
| QVariant(const QRegularExpression &re) | |
| QVariant(const QLocale &l) | |
| QVariant(const QRectF &val) | |
| QVariant(const QRect &val) | |
| QVariant(const QLineF &val) | |
| QVariant(const QLine &val) | |
| QVariant(const QPointF &val) | |
| QVariant(const QPoint &val) | |
| QVariant(const QSizeF &val) | |
| QVariant(const QSize &val) | |
| QVariant(const QHash<QString, QVariant> &val) | |
| QVariant(const QMap<QString, QVariant> &val) | |
| QVariant(const QList<QVariant> &val) | |
| QVariant(const QDateTime &val) | |
| QVariant(QTime val) | |
| QVariant(QDate val) | |
| QVariant(QChar c) | |
| QVariant(const QStringList &val) | |
| QVariant(QLatin1String val) | |
| QVariant(const QString &val) | |
| QVariant(const QBitArray &val) | |
| QVariant(const QByteArray &val) | |
| QVariant(const char *val) | |
| QVariant(float val) | |
| QVariant(double val) | |
| QVariant(bool val) | |
| QVariant(qulonglong val) | |
| QVariant(qlonglong val) | |
| QVariant(uint val) | |
| QVariant(int val) | |
| QVariant(const QVariant &p) | |
| QVariant(QMetaType type, const void *copy = nullptr) | |
| QVariant() | |
| QVariant & | operator=(QVariant &&other) |
| QVariant & | operator=(const QVariant &variant) |
| ~QVariant() | |
| bool | canConvert(QMetaType type) const |
| bool | canConvert() const |
| bool | canView() const |
| void | clear() |
| const void * | constData() const |
| bool | convert(QMetaType targetType) |
| void * | data() |
| const void * | data() const |
| bool | isNull() const |
| bool | isValid() const |
| QMetaType | metaType() const |
| void | setValue(T &&value) |
| void | setValue(const QVariant &value) |
| void | setValue(QVariant &&value) |
| void | swap(QVariant &other) |
| QBitArray | toBitArray() const |
| bool | toBool() const |
| QByteArray | toByteArray() const |
| QChar | 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 |
| qlonglong | toLongLong(bool *ok = nullptr) const |
| QMap<QString, QVariant> | toMap() const |
| QModelIndex | toModelIndex() const |
| QPersistentModelIndex | toPersistentModelIndex() const |
| QPoint | toPoint() const |
| QPointF | toPointF() const |
| qreal | toReal(bool *ok = nullptr) const |
| QRect | toRect() const |
| QRectF | toRectF() const |
| QRegularExpression | toRegularExpression() const |
| QSize | toSize() const |
| QSizeF | toSizeF() const |
| QString | toString() const |
| QStringList | toStringList() const |
| QTime | toTime() const |
| uint | toUInt(bool *ok = nullptr) const |
| qulonglong | toULongLong(bool *ok = nullptr) const |
| QUrl | toUrl() const |
| QUuid | toUuid() const |
| int | typeId() const |
| const char * | typeName() const |
| int | userType() const |
| T | value() const |
| T | view() |
| QPartialOrdering | compare(const QVariant &lhs, const QVariant &rhs) |
| QVariant | fromStdVariant(const std::variant<Types...> &value) |
| QVariant | fromValue(const T &value) |
| QVariantHash | |
| QVariantList | |
| QVariantMap | |
| T | qvariant_cast(const QVariant &value) |
| bool | operator!=(const QVariant &v1, const QVariant &v2) |
| bool | operator==(const QVariant &v1, const QVariant &v2) |
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 typeId() at a time. (Some types 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(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 holds the value 223
v = QVariant(QStringList()); // The variant now holds a 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. A variant is null if the variant contains no initialized value, or contains a null pointer.
QVariant x; // x.isNull() == true QVariant y = QVariant::fromValue(nullptr); // y.isNull() == true
QVariant can be extended to support other types than those mentioned in the QMetaType::Type enum. See Creating Custom Qt Types for details.
Because QVariant is part of the Qt Core module, it cannot provide conversion functions to data types defined in Qt GUI, 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;
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(QMetaType::fromType<int>()) 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.
See also QMetaType.
Returns a pointer to the contained object as a generic void* that cannot be written to.
See also QMetaType.
Returns the storage type of the value stored in the variant. This is the same as metaType().id().
See also metaType().
[since 5.2] QVariant::QVariant(QVariant &&other)
Move-constructs a QVariant instance, making it point at the same object that other was pointing to.
This function was introduced in Qt 5.2.
[since 5.5] QVariant::QVariant(const QPersistentModelIndex &val)
Constructs a new variant with a QPersistentModelIndex value, val.
This function was introduced in Qt 5.5.
[since 5.0] QVariant::QVariant(const QModelIndex &val)
Constructs a new variant with a QModelIndex value, val.
This function was introduced in Qt 5.0.
[since 5.0] QVariant::QVariant(const QJsonDocument &val)
Constructs a new variant with a json document value, val.
This function was introduced in Qt 5.0.
[since 5.0] QVariant::QVariant(const QJsonArray &val)
Constructs a new variant with a json array value, val.
This function was introduced in Qt 5.0.
[since 5.0] QVariant::QVariant(const QJsonObject &val)
Constructs a new variant with a json object value, val.
This function was introduced in Qt 5.0.
[since 5.0] QVariant::QVariant(const QJsonValue &val)
Constructs a new variant with a json value, val.
This function was introduced in Qt 5.0.
Constructs a new variant with a url value of val.
[since 5.0] QVariant::QVariant(const QUuid &val)
Constructs a new variant with an uuid value, val.
This function was introduced in Qt 5.0.
Constructs a new variant with an easing curve value, val.
[since 5.0] QVariant::QVariant(const QRegularExpression &re)
Constructs a new variant with the regular expression value re.
This function was introduced in Qt 5.0.
Constructs a new variant with a locale value, l.
Constructs a new variant with a rect value of val.
Constructs a new variant with a rect value of val.
Constructs a new variant with a line value of val.
Constructs a new variant with a line value of val.
Constructs a new variant with a point value of val.
Constructs a new variant with a point value of val.
Constructs a new variant with a size value of val.
Constructs a new variant with a size value of val.
Constructs a new variant with a hash of QVariants, val.
Constructs a new variant with a map of QVariants, val.
Constructs a new variant with a list value, val.
Constructs a new variant with a date/time value, val.
Constructs a new variant with a time value, val.
Constructs a new variant with a date value, val.
Constructs a new variant with a char value, c.
Constructs a new variant with a string list value, val.
Constructs a new variant with a string value, val.
Constructs a new variant with a string value, val.
Constructs a new variant with a bitarray value, val.
Constructs a new variant with a bytearray value, val.
Constructs a new variant with a string value of val. The variant creates a deep copy of val into a QString assuming UTF-8 encoding on the input val.
Note that val is converted to a QString for storing in the variant and QVariant::userType() will return QMetaType::QString for the variant.
You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications.
Constructs a new variant with a floating point value, val.
Constructs a new variant with a floating point value, val.
Constructs a new variant with a boolean value, val.
Constructs a new variant with an unsigned long long integer value, val.
Constructs a new variant with a long long integer value, val.
Constructs a new variant with an unsigned integer value, val.
Constructs a new variant with an integer value, val.
Constructs a copy of the variant, p, passed as the argument to this constructor.
Constructs variant of type type, and initializes with copy if copy is not nullptr.
Note that you have to pass the address of the variable you want stored.
Usually, you never have to use this constructor, use QVariant::fromValue() instead to construct variants from the pointer types represented by QMetaType::VoidStar, and QMetaType::QObjectStar.
See also QVariant::fromValue() and QMetaType::Type.
Constructs an invalid variant.
[since 5.2] QVariant &QVariant::operator=(QVariant &&other)
Move-assigns other to this QVariant instance.
This function was introduced in Qt 5.2.
Assigns the value of the variant variant to this variant.
Destroys the QVariant and the contained object.
Note that subclasses that reimplement clear() should reimplement the destructor to call clear(). This destructor calls clear(), but because it is the destructor, QVariant::clear() is called rather than a subclass's clear().
[since 6.0] bool QVariant::canConvert(QMetaType type) const
Returns true if the variant's type can be cast to the requested type, type. Such casting is done automatically when calling the toInt(), toBool(), ... methods.
This function was introduced in Qt 6.0.
See also QMetaType::canConvert().
Returns true if the variant can be converted to the template type T, otherwise false.
Example:
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
A QVariant containing a pointer to a type derived from QObject will also return true for this function if a qobject_cast to the template type T would succeed. Note that this only works for QObject subclasses which use the Q_OBJECT macro.
See also convert().
Returns true if a mutable view of the template type T can be created on this variant, otherwise false.
See also value().
Convert this variant to type QMetaType::UnknownType and free up any resources used.
[static, since 6.0] QPartialOrdering QVariant::compare(const QVariant &lhs, const QVariant &rhs)
Compares the objects at lhs and rhs for ordering.
Returns QPartialOrdering::Unordered if comparison is not supported or the values are unordered. Otherwise, returns QPartialOrdering::Less, QPartialOrdering::Equivalent or QPartialOrdering::Greater if lhs is less than, equivalent to or greater than rhs, respectively.
If the variants contain data with a different metatype, the values are considered unordered unless they are both of numeric or pointer types, where regular numeric or pointer comparison rules will be used.
Note: : If a numeric comparison is done and at least one value is NaN, QPartialOrdering::Unordered is returned.
If both variants contain data of the same metatype, the method will use the QMetaType::compare method to determine the ordering of the two variants, which can also indicate that it can't establish an ordering between the two values.
This function was introduced in Qt 6.0.
See also QMetaType::compare() and QMetaType::isOrdered().
[since 6.0] bool QVariant::convert(QMetaType targetType)
Casts the variant to the requested type, targetType. If the cast cannot be done, the variant is still changed to the requested type, but is left in a cleared null state similar to that constructed by QVariant(Type).
Returns true if the current type of the variant was successfully cast; otherwise returns false.
A QVariant containing a pointer to a type derived from QObject will also convert and return true for this function if a qobject_cast to the type described by targetType would succeed. Note that this only works for QObject subclasses which use the Q_OBJECT macro.
Note: converting QVariants that are null due to not being initialized or having failed a previous conversion will always fail, changing the type, remaining null, and returning false.
This function was introduced in Qt 6.0.
See also canConvert() and clear().
Returns a pointer to the contained object as a generic void* that can be written to.
This function detaches the QVariant. When called on a null-QVariant, the QVariant will not be null after the call.
See also QMetaType.
[static, since 5.11] template <typename Types> QVariant QVariant::fromStdVariant(const std::variant<Types...> &value)
Returns a QVariant with the type and value of the active variant of value. If the active type is std::monostate a default QVariant is returned.
Note: With this method you do not need to register the variant as a Qt metatype, since the std::variant is resolved before being stored. The component types should be registered however.
This function was introduced in Qt 5.11.
See also fromValue().
[static] template <typename T> QVariant QVariant::fromValue(const T &value)
Returns a QVariant containing a copy of value. Behaves exactly like setValue() otherwise.
Example:
MyCustomStruct s; return QVariant::fromValue(s);
Note: If you are working with custom types, you should use the Q_DECLARE_METATYPE() macro to register your custom type.
See also setValue() and value().
Returns true if this is a null variant, false otherwise.
A variant is considered null if it contains no initialized value or a null pointer.
Note: This behavior has been changed from Qt 5, where isNull() would also return true if the variant contained an object of a builtin type with an isNull() method that returned true for that object.
See also convert().
Returns true if the storage type of this variant is not QMetaType::UnknownType; otherwise returns false.
[since 6.0] QMetaType QVariant::metaType() const
Returns the QMetaType of the value stored in the variant.
This function was introduced in Qt 6.0.
Stores a copy of value. If T is a type that QVariant doesn't support, QMetaType is used to store the value. A compile error will occur if QMetaType doesn't handle the type.
Example:
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(), and canConvert().
Copies value over this QVariant. It is equivalent to simply assigning value to this QVariant.
Moves value over this QVariant. It is equivalent to simply move assigning value to this QVariant.
Swaps variant other with this variant. This operation is very fast and never fails.
Returns the variant as a QBitArray if the variant has userType() QMetaType::QBitArray; otherwise returns an empty bit array.
See also canConvert() and convert().
Returns the variant as a bool if the variant has userType() Bool.
Returns true if the variant has userType() QMetaType::Bool, QMetaType::QChar, QMetaType::Double, QMetaType::Int, QMetaType::LongLong, QMetaType::UInt, or QMetaType::ULongLong and the value is non-zero, or if the variant has type QMetaType::QString or QMetaType::QByteArray and its lower-case content is not one of the following: empty, "0" or "false"; otherwise returns false.
See also canConvert() and convert().
Returns the variant as a QByteArray if the variant has userType() QMetaType::QByteArray or QMetaType::QString (converted using QString::fromUtf8()); otherwise returns an empty byte array.
See also canConvert() and convert().
Returns the variant as a QChar if the variant has userType() QMetaType::QChar, QMetaType::Int, or QMetaType::UInt; otherwise returns an invalid QChar.
See also canConvert() and convert().
Returns the variant as a QDate if the variant has userType() QMetaType::QDate, QMetaType::QDateTime, or QMetaType::QString; otherwise returns an invalid date.
If the type() is QMetaType::QString, an invalid date will be returned if the string cannot be parsed as a Qt::ISODate format date.
See also canConvert() and convert().
Returns the variant as a QDateTime if the variant has userType() QMetaType::QDateTime, QMetaType::QDate, or QMetaType::QString; otherwise returns an invalid date/time.
If the type() is QMetaType::QString, an invalid date/time will be returned if the string cannot be parsed as a Qt::ISODate format date/time.
See also canConvert() and convert().
Returns the variant as a double if the variant has userType() QMetaType::Double, QMetaType::Float, QMetaType::Bool, QMetaType::QByteArray, QMetaType::Int, QMetaType::LongLong, QMetaType::QString, QMetaType::UInt, or QMetaType::ULongLong; otherwise returns 0.0.
If ok is non-null: *ok is set to true if the value could be converted to a double; otherwise *ok is set to false.
See also canConvert() and convert().
Returns the variant as a QEasingCurve if the variant has userType() QMetaType::QEasingCurve; otherwise returns a default easing curve.
See also canConvert() and convert().
Returns the variant as a float if the variant has userType() QMetaType::Double, QMetaType::Float, QMetaType::Bool, QMetaType::QByteArray, QMetaType::Int, QMetaType::LongLong, QMetaType::QString, QMetaType::UInt, or QMetaType::ULongLong; otherwise returns 0.0.
If ok is non-null: *ok is set to true if the value could be converted to a double; otherwise *ok is set to false.
See also canConvert() and convert().
Returns the variant as a QHash<QString, QVariant> if the variant has type() QMetaType::QVariantHash; otherwise returns an empty map.
See also canConvert() and convert().
Returns the variant as an int if the variant has userType() QMetaType::Int, QMetaType::Bool, QMetaType::QByteArray, QMetaType::QChar, QMetaType::Double, QMetaType::LongLong, QMetaType::QString, QMetaType::UInt, or QMetaType::ULongLong; otherwise returns 0.
If ok is non-null: *ok is set to true if the value could be converted to an int; otherwise *ok is set to false.
Warning: If the value is convertible to a QMetaType::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 QString::toInt().
See also canConvert() and convert().
[since 5.0] QJsonArray QVariant::toJsonArray() const
Returns the variant as a QJsonArray if the variant has userType() QJsonArray; otherwise returns a default constructed QJsonArray.
This function was introduced in Qt 5.0.
See also canConvert() and convert().
[since 5.0] QJsonDocument QVariant::toJsonDocument() const
Returns the variant as a QJsonDocument if the variant has userType() QJsonDocument; otherwise returns a default constructed QJsonDocument.
This function was introduced in Qt 5.0.
See also canConvert() and convert().
[since 5.0] QJsonObject QVariant::toJsonObject() const
Returns the variant as a QJsonObject if the variant has userType() QJsonObject; otherwise returns a default constructed QJsonObject.
This function was introduced in Qt 5.0.
See also canConvert() and convert().
[since 5.0] QJsonValue QVariant::toJsonValue() const
Returns the variant as a QJsonValue if the variant has userType() QJsonValue; otherwise returns a default constructed QJsonValue.
This function was introduced in Qt 5.0.
See also canConvert() and convert().
Returns the variant as a QLine if the variant has userType() QMetaType::QLine; otherwise returns an invalid QLine.
See also canConvert() and convert().
Returns the variant as a QLineF if the variant has userType() QMetaType::QLineF; otherwise returns an invalid QLineF.
See also canConvert() and convert().
Returns the variant as a QVariantList if the variant has userType() QMetaType::QVariantList or QMetaType::QStringList; otherwise returns an empty list.
See also canConvert() and convert().
Returns the variant as a QLocale if the variant has userType() QMetaType::QLocale; otherwise returns an invalid QLocale.
See also canConvert() and convert().
Returns the variant as a long long int if the variant has userType() QMetaType::LongLong, QMetaType::Bool, QMetaType::QByteArray, QMetaType::QChar, QMetaType::Double, QMetaType::Int, QMetaType::QString, QMetaType::UInt, or QMetaType::ULongLong; otherwise returns 0.
If ok is non-null: *ok is set to true if the value could be converted to an int; otherwise *ok is set to false.
See also canConvert() and convert().
Returns the variant as a QMap<QString, QVariant> if the variant has type() QMetaType::QVariantMap; otherwise returns an empty map.
See also canConvert() and convert().
[since 5.0] QModelIndex QVariant::toModelIndex() const
Returns the variant as a QModelIndex if the variant has userType() QModelIndex; otherwise returns a default constructed QModelIndex.
This function was introduced in Qt 5.0.
See also canConvert(), convert(), and toPersistentModelIndex().
[since 5.5] QPersistentModelIndex QVariant::toPersistentModelIndex() const
Returns the variant as a QPersistentModelIndex if the variant has userType() QPersistentModelIndex; otherwise returns a default constructed QPersistentModelIndex.
This function was introduced in Qt 5.5.
See also canConvert(), convert(), and toModelIndex().
Returns the variant as a QPoint if the variant has userType() QMetaType::QPoint or QMetaType::QPointF; otherwise returns a null QPoint.
See also canConvert() and convert().
Returns the variant as a QPointF if the variant has userType() QMetaType::QPoint or QMetaType::QPointF; otherwise returns a null QPointF.
See also canConvert() and convert().
Returns the variant as a qreal if the variant has userType() QMetaType::Double, QMetaType::Float, QMetaType::Bool, QMetaType::QByteArray, QMetaType::Int, QMetaType::LongLong, QMetaType::QString, QMetaType::UInt, or QMetaType::ULongLong; otherwise returns 0.0.
If ok is non-null: *ok is set to true if the value could be converted to a double; otherwise *ok is set to false.
See also canConvert() and convert().
Returns the variant as a QRect if the variant has userType() QMetaType::QRect; otherwise returns an invalid QRect.
See also canConvert() and convert().
Returns the variant as a QRectF if the variant has userType() QMetaType::QRect or QMetaType::QRectF; otherwise returns an invalid QRectF.
See also canConvert() and convert().
[since 5.0] QRegularExpression QVariant::toRegularExpression() const
Returns the variant as a QRegularExpression if the variant has userType() QRegularExpression; otherwise returns an empty QRegularExpression.
This function was introduced in Qt 5.0.
See also canConvert() and convert().
Returns the variant as a QSize if the variant has userType() QMetaType::QSize; otherwise returns an invalid QSize.
See also canConvert() and convert().
Returns the variant as a QSizeF if the variant has userType() QMetaType::QSizeF; otherwise returns an invalid QSizeF.
See also canConvert() and convert().
Returns the variant as a QString if the variant has a userType() including, but not limited to:
QMetaType::QString, QMetaType::Bool, QMetaType::QByteArray, QMetaType::QChar, QMetaType::QDate, QMetaType::QDateTime, QMetaType::Double, QMetaType::Int, QMetaType::LongLong, QMetaType::QStringList, QMetaType::QTime, QMetaType::UInt, or QMetaType::ULongLong.
Calling QVariant::toString() on an unsupported variant returns an empty string.
See also canConvert() and convert().
Returns the variant as a QStringList if the variant has userType() QMetaType::QStringList, QMetaType::QString, or QMetaType::QVariantList of a type that can be converted to QString; otherwise returns an empty list.
See also canConvert() and convert().
Returns the variant as a QTime if the variant has userType() QMetaType::QTime, QMetaType::QDateTime, or QMetaType::QString; otherwise returns an invalid time.
If the type() is QMetaType::QString, an invalid time will be returned if the string cannot be parsed as a Qt::ISODate format time.
See also canConvert() and convert().
Returns the variant as an unsigned int if the variant has userType() QMetaType::UInt, QMetaType::Bool, QMetaType::QByteArray, QMetaType::QChar, QMetaType::Double, QMetaType::Int, QMetaType::LongLong, QMetaType::QString, or QMetaType::ULongLong; otherwise returns 0.
If ok is non-null: *ok is set to true if the value could be converted to an unsigned int; otherwise *ok is set to false.
Warning: If the value is convertible to a QMetaType::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() and convert().
Returns the variant as an unsigned long long int if the variant has type() QMetaType::ULongLong, QMetaType::Bool, QMetaType::QByteArray, QMetaType::QChar, QMetaType::Double, QMetaType::Int, QMetaType::LongLong, QMetaType::QString, or QMetaType::UInt; otherwise returns 0.
If ok is non-null: *ok is set to true if the value could be converted to an int; otherwise *ok is set to false.
See also canConvert() and convert().
Returns the variant as a QUrl if the variant has userType() QMetaType::QUrl; otherwise returns an invalid QUrl.
See also canConvert() and convert().
[since 5.0] QUuid QVariant::toUuid() const
Returns the variant as a QUuid if the variant has type() QMetaType::QUuid, QMetaType::QByteArray or QMetaType::QString; otherwise returns a default-constructed QUuid.
This function was introduced in Qt 5.0.
See also canConvert() and convert().
Returns the name of the type stored in the variant. The returned strings describe the C++ datatype used to store the data: for example, "QFont", "QString", or "QVariantList". An Invalid variant returns 0.
Returns the stored value converted to the template type T. Call canConvert() to find out whether a type can be converted. If the value cannot be converted, a default-constructed value will be returned.
If the type T is supported by QVariant, this function behaves exactly as toString(), toInt() etc.
Example:
QVariant v;
MyCustomStruct c;
if (v.canConvert<MyCustomStruct>())
c = v.value<MyCustomStruct>();
v = 7;
int i = v.value<int>(); // same as v.toInt()
QString s = v.value<QString>(); // same as v.toString(), s is now "7"
MyCustomStruct c2 = v.value<MyCustomStruct>(); // conversion failed, c2 is empty If the QVariant contains a pointer to a type derived from QObject then T may be any QObject type. If the pointer stored in the QVariant can be qobject_cast to T, then that result is returned. Otherwise nullptr is returned. Note that this only works for QObject subclasses which use the Q_OBJECT macro.
If the QVariant contains a sequential container and T is QVariantList, the elements of the container will be converted into QVariants and returned as a QVariantList.
QList<int> intList = {7, 11, 42};
QVariant variant = QVariant::fromValue(intList);
if (variant.canConvert<QVariantList>()) {
QSequentialIterable iterable = variant.value<QSequentialIterable>();
// Can use foreach:
foreach (const QVariant &v, iterable) {
qDebug() << v;
}
// Can use C++11 range-for:
for (const QVariant &v : iterable) {
qDebug() << v;
}
// Can use iterators:
QSequentialIterable::const_iterator it = iterable.begin();
const QSequentialIterable::const_iterator end = iterable.end();
for ( ; it != end; ++it) {
qDebug() << *it;
}
} See also setValue(), fromValue(), canConvert(), and Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE().
Returns a mutable view of template type T on the stored value. Call canView() to find out whether such a view is supported. If no such view can be created, returns the stored value converted to the template type T. Call canConvert() to find out whether a type can be converted. If the value can neither be viewed nor converted, a default-constructed value will be returned.
See also canView() and Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE().
[alias] QVariantHash
Synonym for QHash<QString, QVariant>.
[alias] QVariantList
[alias] QVariantMap
Synonym for QMap<QString, QVariant>.
Returns the given value converted to the template type T.
This function is equivalent to QVariant::value().
See also QVariant::value().
Returns false if v1 and v2 are equal; otherwise returns true.
QVariant uses the equality operator of the type() contained to check for equality.
Variants of different types will always compare as not equal with a few exceptions:
Returns true if v1 and v2 are equal; otherwise returns false.
QVariant uses the equality operator of the type() contained to check for equality.
Variants of different types will always compare as not equal with a few exceptions:
The result of the function is not affected by the result of QVariant::isNull, which means that two values can be equal even if one of them is null and another is not.
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Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-6.2/qvariant.html