QThreadStorage Class Reference
[QtCore module]

Detailed Description

The QThreadStorage class provides per-thread data storage.

QThreadStorage is a template class that provides per-thread data storage.

Note that due to compiler limitations, QThreadStorage can only store pointers.

The setLocalData() function stores a single thread-specific value for the calling thread. The data can be accessed later using localData(). 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.

The hasLocalData() function allows the programmer to determine if data has previously been set using the setLocalData() function. This is also useful for lazy initializiation.

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)
 {
     if (!caches.hasLocalData())
         caches.setLocalData(new QCache<QString, SomeClass>);

     caches.localData()->insert(key, object);
 }

 void removeFromCache(const QString &key)
 {
     if (!caches.hasLocalData())
         return;

     caches.localData()->remove(key);
 }