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QReadLocker Class Reference
^{[QtCore module]}

The QReadLocker class is a convenience class that simplifies locking and unlocking read-write locks for read 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 QReadLocker (and QWriteLocker) is to simplify QReadWriteLock locking and unlocking. Locking and unlocking statements or in exception handling code is error-prone and difficult to debug. QReadLocker can be used in such situations to ensure that the state of the lock is always well-defined.

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

 QReadWriteLock lock;

 QByteArray readData()
 {
     QReadLocker locker(&lock);
     ...
     return data;
 }

It is equivalent to the following code:

 QReadWriteLock lock;

 QByteArray readData()
 {
     lock.lockForRead();
     ...
     lock.unlock();
     return data;
 }

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

Method Documentation

QReadLocker.__init__ (self, QReadWriteLock areadWriteLock)

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

See also QReadWriteLock.lockForRead().

QReadWriteLock QReadLocker.readWriteLock (self)

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

QReadLocker.relock (self)

Relocks an unlocked lock.

See also unlock().

QReadLocker.unlock (self)

Unlocks the lock associated with this locker.

See also QReadWriteLock.unlock().

object QReadLocker.__enter__ (self)

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