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QWriteLocker Class Reference
^{[QtCore module]}

The QWriteLocker class is a convenience class that simplifies locking and unlocking read-write locks for write access. More...

Methods

• __init__ (self, QReadWriteLock areadWriteLock)
• QReadWriteLock readWriteLock (self)
• relock (self)
• unlock (self)

Special Methods

• object __enter__ (self)
• __exit__ (self, object type, object value, object traceback)

The purpose of QWriteLocker (and QReadLocker is to simplify QReadWriteLock locking and unlocking. Locking and unlocking statements or in exception handling code is error-prone and difficult to debug. QWriteLocker can be used in such situations to ensure that the state of the lock is always well-defined.

Here's an example that uses QWriteLocker to lock and unlock a read-write lock for writing:

 QReadWriteLock lock;

 void writeData(const QByteArray &data)
 {
     QWriteLocker locker(&lock);
     ...
 }

It is equivalent to the following code:

 QReadWriteLock lock;

 void writeData(const QByteArray &data)
 {
     lock.lockForWrite();
     ...
     lock.unlock();
 }

The QMutexLocker documentation shows examples where the use of a locker object greatly simplifies programming.

Method Documentation

QWriteLocker.__init__ (self, QReadWriteLock areadWriteLock)

Constructs a QWriteLocker and locks lock for writing. The lock will be unlocked when the QWriteLocker is destroyed. If lock is zero, QWriteLocker does nothing.

See also QReadWriteLock.lockForWrite().

QReadWriteLock QWriteLocker.readWriteLock (self)

Returns a pointer to the read-write lock that was passed to the constructor.

QWriteLocker.relock (self)

Relocks an unlocked lock.

See also unlock().

QWriteLocker.unlock (self)

Unlocks the lock associated with this locker.

See also QReadWriteLock.unlock().

object QWriteLocker.__enter__ (self)

QWriteLocker.__exit__ (self, object type, object value, object traceback)