The QThreadStorage class provides per-thread data storage. More...
Header: | #include <QThreadStorage> |
CMake: | find_package(Qt6 COMPONENTS Core REQUIRED) target_link_libraries(mytarget PRIVATE Qt6::Core) |
qmake: | QT += core |
Note: All functions in this class are thread-safe.
QThreadStorage() | |
~QThreadStorage() | |
bool | hasLocalData() const |
T & | localData() |
T | localData() const |
void | setLocalData(T data) |
QThreadStorage is a template class that provides per-thread data storage.
The setLocalData() function stores a single thread-specific value for the calling thread. The data can be accessed later using localData().
The hasLocalData() function allows the programmer to determine if data has previously been set using the setLocalData() function. This is also useful for lazy initialization.
If T is a pointer type, QThreadStorage takes ownership of the data (which must be created on the heap with new
) and deletes it when the thread exits, either normally or via termination.
For example, the following code uses QThreadStorage to store a single cache for each thread that calls the cacheObject() and removeFromCache() functions. The cache is automatically deleted when the calling thread exits.
QThreadStorage<QCache<QString, SomeClass> > caches; void cacheObject(const QString &key, SomeClass *object) { caches.localData().insert(key, object); } void removeFromCache(const QString &key) { if (!caches.hasLocalData()) return; caches.localData().remove(key); }
main()
thread. QThreadStorage deletes all data set for the main()
thread when QApplication is destroyed, regardless of whether or not the main()
thread has actually finished.See also QThread.
Constructs a new per-thread data storage object.
Destroys the per-thread data storage object.
Note: The per-thread data stored is not deleted. Any data left in QThreadStorage is leaked. Make sure that all threads using QThreadStorage have exited before deleting the QThreadStorage.
See also hasLocalData().
If T is a pointer type, returns true
if the calling thread has non-zero data available.
If T is a value type, returns whether the data has already been constructed by calling setLocalData or localData.
See also localData().
Returns a reference to the data that was set by the calling thread.
If no data has been set, this will create a default constructed instance of type T.
See also setLocalData() and hasLocalData().
This is an overloaded function.
Returns a copy of the data that was set by the calling thread.
See also hasLocalData().
Sets the local data for the calling thread to data. It can be accessed later using the localData() functions.
If T is a pointer type, QThreadStorage takes ownership of the data and deletes it automatically either when the thread exits (either normally or via termination) or when setLocalData() is called again.
See also localData() and hasLocalData().
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Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-6.2/qthreadstorage.html