QWriteLocker

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

 #include <QWriteLocker>

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

Public Functions

QWriteLocker ( QReadWriteLock * lock )
~QWriteLocker ()
QReadWriteLock * readWriteLock () const
void relock ()
void unlock ()

Detailed Description

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

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.

See also QReadLocker and QReadWriteLock.

Member Function Documentation

QWriteLocker::QWriteLocker ( QReadWriteLock * lock )

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().

QWriteLocker::~QWriteLocker ()

Destroys the QWriteLocker and unlocks the lock that was passed to the constructor.

See also QReadWriteLock::unlock().

QReadWriteLock * QWriteLocker::readWriteLock () const

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

void QWriteLocker::relock ()

Relocks an unlocked lock.

See also unlock().

void QWriteLocker::unlock ()

Unlocks the lock associated with this locker.

See also QReadWriteLock::unlock().

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