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/Qt 5.11

QReadLocker Class

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

Header: #include <QReadLocker>
qmake: QT += core

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

Public Functions

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

Detailed Description

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

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.

See also QWriteLocker and QReadWriteLock.

Member Function Documentation

QReadLocker::QReadLocker(QReadWriteLock *lock)

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().

QReadLocker::~QReadLocker()

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

See also QReadWriteLock::unlock().

QReadWriteLock *QReadLocker::readWriteLock() const

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

void QReadLocker::relock()

Relocks an unlocked lock.

See also unlock().

void QReadLocker::unlock()

Unlocks the lock associated with this locker.

See also QReadWriteLock::unlock().

© The Qt Company Ltd
Licensed under the GNU Free Documentation License, Version 1.3.
https://doc.qt.io/qt-5/qreadlocker.html