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<td width="1"> </td><td class="postheader" valign="center"><a href="index.html"><font color="#004faf">Home</font></a> · <a href="classes.html"><font color="#004faf">All Classes</font></a> · <a href="functions.html"><font color="#004faf">All Functions</font></a> · <a href="overviews.html"><font color="#004faf">Overviews</font></a></td></tr></table><h1 class="title">QReadLocker Class Reference<br /><span class="small-subtitle">[<a href="qtcore.html">QtCore</a> module]</span>
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<p>The QReadLocker class is a convenience class that simplifies locking and unlocking read-write locks for read access. <a href="#details">More...</a></p>
<pre> #include <QReadLocker></pre><p><b>Note:</b> All functions in this class are <a href="threads-reentrancy.html#thread-safe">thread-safe</a>.</p>
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<li><a href="qreadlocker-members.html">List of all members, including inherited members</a></li>
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<h2>Public Functions</h2>
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<tr><td class="memItemLeft" align="right" valign="top"></td><td class="memItemRight" valign="bottom"><b><a href="qreadlocker.html#QReadLocker">QReadLocker</a></b> ( QReadWriteLock * <i>lock</i> )</td></tr>
<tr><td class="memItemLeft" align="right" valign="top"></td><td class="memItemRight" valign="bottom"><b><a href="qreadlocker.html#dtor.QReadLocker">~QReadLocker</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">QReadWriteLock * </td><td class="memItemRight" valign="bottom"><b><a href="qreadlocker.html#readWriteLock">readWriteLock</a></b> () const</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qreadlocker.html#relock">relock</a></b> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><b><a href="qreadlocker.html#unlock">unlock</a></b> ()</td></tr>
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<h2>Detailed Description</h2>
<p>The QReadLocker class is a convenience class that simplifies locking and unlocking read-write locks for read access.</p>
<p>The purpose of QReadLocker (and <a href="qwritelocker.html">QWriteLocker</a>) is to simplify <a href="qreadwritelock.html">QReadWriteLock</a> 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.</p>
<p>Here's an example that uses QReadLocker to lock and unlock a read-write lock for reading:</p>
<pre> QReadWriteLock lock;
QByteArray readData()
{
QReadLocker locker(&lock);
...
return data;
}</pre>
<p>It is equivalent to the following code:</p>
<pre> QReadWriteLock lock;
QByteArray readData()
{
lock.lockForRead();
...
lock.unlock();
return data;
}</pre>
<p>The <a href="qmutexlocker.html">QMutexLocker</a> documentation shows examples where the use of a locker object greatly simplifies programming.</p>
<p>See also <a href="qwritelocker.html">QWriteLocker</a> and <a href="qreadwritelock.html">QReadWriteLock</a>.</p>
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<h2>Member Function Documentation</h2>
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<h3 class="fn"><a name="QReadLocker"></a>QReadLocker::QReadLocker ( <a href="qreadwritelock.html">QReadWriteLock</a> * <i>lock</i> )</h3>
<p>Constructs a <a href="qreadlocker.html">QReadLocker</a> and locks <i>lock</i> for reading. The lock will be unlocked when the <a href="qreadlocker.html">QReadLocker</a> is destroyed. If <tt>lock</tt> is zero, <a href="qreadlocker.html">QReadLocker</a> does nothing.</p>
<p>See also <a href="qreadwritelock.html#lockForRead">QReadWriteLock::lockForRead</a>().</p>
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<h3 class="fn"><a name="dtor.QReadLocker"></a>QReadLocker::~QReadLocker ()</h3>
<p>Destroys the <a href="qreadlocker.html">QReadLocker</a> and unlocks the lock that was passed to the constructor.</p>
<p>See also <a href="qreadwritelock.html#unlock">QReadWriteLock::unlock</a>().</p>
<a name="//apple_ref/cpp/instm/QReadLocker/readWriteLock"></a>
<h3 class="fn"><a name="readWriteLock"></a><a href="qreadwritelock.html">QReadWriteLock</a> * QReadLocker::readWriteLock () const</h3>
<p>Returns a pointer to the read-write lock that was passed to the constructor.</p>
<a name="//apple_ref/cpp/instm/QReadLocker/relock"></a>
<h3 class="fn"><a name="relock"></a>void QReadLocker::relock ()</h3>
<p>Relocks an unlocked lock.</p>
<p>See also <a href="qreadlocker.html#unlock">unlock</a>().</p>
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<h3 class="fn"><a name="unlock"></a>void QReadLocker::unlock ()</h3>
<p>Unlocks the lock associated with this locker.</p>
<p>See also <a href="qreadwritelock.html#unlock">QReadWriteLock::unlock</a>().</p>
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