QThreadStorage

The QThreadStorage class provides per-thread data storage. More...

 #include <QThreadStorage>

Note: All functions in this class are thread-safe.

Public Functions

QThreadStorage ()
~QThreadStorage ()
bool hasLocalData () const
T & localData ()
T localData () const
void setLocalData ( T data )

Detailed Description

The QThreadStorage class provides per-thread data storage.

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 initializiation.

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);
 }

Caveats

See also QThread.

Last modified: 2014-03-13

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