QMetaType Class

 int id = QMetaType::type("MyClass");
 if (id != QMetaType::UnknownType) {
     void *myClassPtr = QMetaType::create(id);
     ...
     QMetaType::destroy(id, myClassPtr);
     myClassPtr = 0;
 }

Member Function Documentation

QMetaType::QMetaType(const int type)

QMetaType::~QMetaType()

void * QMetaType::construct(int type, void * where, const void * copy) [static]

Constructs a value of the given type in the existing memory addressed by where, that is a copy of copy, and returns where. If copy is zero, the value is default constructed.

This is a low-level function for explicitly managing the memory used to store the type. Consider calling create() if you don't need this level of control (that is, use "new" rather than "placement new").

You must ensure that where points to a location that can store a value of type type, and that where is suitably aligned. The type's size can be queried by calling sizeOf().

The rule of thumb for alignment is that a type is aligned to its natural boundary, which is the smallest power of 2 that is bigger than the type, unless that alignment is larger than the maximum useful alignment for the platform. For practical purposes, alignment larger than 2 * sizeof(void*) is only necessary for special hardware instructions (e.g., aligned SSE loads and stores on x86).

This function was introduced in Qt 5.0.

See also destruct() and sizeOf().

void * QMetaType::construct(void * where, const void * copy = 0) const

void * QMetaType::create(int type, const void * copy = 0) [static]

Returns a copy of copy, assuming it is of type type. If copy is zero, creates a default type.

See also destroy(), isRegistered(), and Type.

void * QMetaType::create(const void * copy = 0) const

void QMetaType::destroy(int type, void * data) [static]

Destroys the data, assuming it is of the type given.

See also create(), isRegistered(), and Type.

void QMetaType::destroy(void * data) const

void QMetaType::destruct(int type, void * where) [static]

Destructs the value of the given type, located at where.

Unlike destroy(), this function only invokes the type's destructor, it doesn't invoke the delete operator.

This function was introduced in Qt 5.0.

See also construct().

void QMetaType::destruct(void * data) const

TypeFlags QMetaType::flags() const

bool QMetaType::isRegistered(int type) [static]

Returns true if the datatype with ID type is registered; otherwise returns false.

See also type(), typeName(), and Type.

bool QMetaType::isRegistered() const

bool QMetaType::isValid() const

bool QMetaType::load(QDataStream & stream, int type, void * data) [static]

Reads the object of the specified type from the given stream into data. Returns true if the object is loaded successfully; otherwise returns false.

The type must have been registered with qRegisterMetaType() and qRegisterMetaTypeStreamOperators() beforehand.

Normally, you should not need to call this function directly. Instead, use QVariant's operator>>(), which relies on load() to stream custom types.

See also save() and qRegisterMetaTypeStreamOperators().

int QMetaType::registerNormalizedType(const QT_PREPEND_NAMESPACE) [static]

int QMetaType::registerNormalizedTypedef(const QT_PREPEND_NAMESPACE) [static]

bool QMetaType::save(QDataStream & stream, int type, const void * data) [static]

Writes the object pointed to by data with the ID type to the given stream. Returns true if the object is saved successfully; otherwise returns false.

The type must have been registered with qRegisterMetaType() and qRegisterMetaTypeStreamOperators() beforehand.

Normally, you should not need to call this function directly. Instead, use QVariant's operator<<(), which relies on save() to stream custom types.

See also load() and qRegisterMetaTypeStreamOperators().

int QMetaType::sizeOf(int type) [static]

Returns the size of the given type in bytes (i.e., sizeof(T), where T is the actual type identified by the type argument).

This function is typically used together with construct() to perform low-level management of the memory used by a type.

This function was introduced in Qt 5.0.

See also construct().

int QMetaType::sizeOf() const

int QMetaType::type(const char * typeName) [static]

Returns a handle to the type called typeName, or QMetaType::UnknownType if there is no such type.

See also isRegistered(), typeName(), and Type.

TypeFlags QMetaType::typeFlags(int type) [static]

Returns flags of the given type.

This function was introduced in Qt 5.0.

See also TypeFlags().

const char * QMetaType::typeName(int typeId) [static]

Returns the type name associated with the given type, or 0 if no matching type was found. The returned pointer must not be deleted.

See also type(), isRegistered(), and Type.

 struct MyStruct
 {
     int i;
     ...
 };

 Q_DECLARE_METATYPE(MyStruct)

 namespace MyNamespace
 {
     ...
 }

 Q_DECLARE_METATYPE(MyNamespace::MyStruct)

 MyStruct s;
 QVariant var;
 var.setValue(s); // copy s into the variant

 ...

 // retrieve the value
 MyStruct s2 = var.value<MyStruct>();