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<td >Qt 5.9</td><td ><a href="qtxmlpatterns-index.html">Qt XML Patterns</a></td><td ><a href="qtxmlpatterns-module.html">C++ Classes</a></td><td >QAbstractMessageHandler</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td>
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<h3><a name="toc">Contents</a></h3>
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<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#protected-functions">Protected Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
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<h1 class="title">QAbstractMessageHandler Class</h1>
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<p>The <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a> class provides a callback interface for handling messages. <a href="#details">More...</a></p>
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<tr><td class="memItemLeft rightAlign topAlign"> Header:</td><td class="memItemRight bottomAlign"> <span class="preprocessor">#include <QAbstractMessageHandler></span>
</td></tr><tr><td class="memItemLeft rightAlign topAlign"> qmake:</td><td class="memItemRight bottomAlign"> QT += xmlpatterns</td></tr><tr><td class="memItemLeft rightAlign topAlign"> Since:</td><td class="memItemRight bottomAlign"> Qt 4.4</td></tr></table></div><ul>
<li><a href="qabstractmessagehandler-members.html">List of all members, including inherited members</a></li>
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<h2 id="public-functions">Public Functions</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qabstractmessagehandler.html#QAbstractMessageHandler">QAbstractMessageHandler</a></b>(QObject *<i>parent</i> = Q_NULLPTR)</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> virtual </td><td class="memItemRight bottomAlign"><b><a href="qabstractmessagehandler.html#dtor.QAbstractMessageHandler">~QAbstractMessageHandler</a></b>()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qabstractmessagehandler.html#message">message</a></b>(QtMsgType <i>type</i>, const QString &<i>description</i>, const QUrl &<i>identifier</i> = QUrl(), const QSourceLocation &<i>sourceLocation</i> = QSourceLocation())</td></tr>
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<h2 id="protected-functions">Protected Functions</h2>
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<tr><td class="memItemLeft rightAlign topAlign"> virtual void </td><td class="memItemRight bottomAlign"><b><a href="qabstractmessagehandler.html#handleMessage">handleMessage</a></b>(QtMsgType <i>type</i>, const QString &<i>description</i>, const QUrl &<i>identifier</i>, const QSourceLocation &<i>sourceLocation</i>) = 0</td></tr>
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<h2 id="details">Detailed Description</h2>
<p>The <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a> class provides a callback interface for handling messages.</p>
<p><a href="qabstractmessagehandler.html">QAbstractMessageHandler</a> is an abstract base class that provides a callback interface for handling messages. For example, class <a href="qxmlquery.html">QXmlQuery</a> parses and runs an <a href="xmlprocessing.html">XQuery</a>. When it detects a compile or runtime error, it generates an appropriate error message, but rather than output the message itself, it passes the message to the <a href="qabstractmessagehandler.html#message">message</a>() function of its <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a>. See <a href="qxmlquery.html#setMessageHandler">QXmlQuery::setMessageHandler</a>().</p>
<p>You create a message handler by subclassing <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a> and implementing <a href="qabstractmessagehandler.html#handleMessage">handleMessage</a>(). You then pass a pointer to an instance of your subclass to any classes that must generate messages. The messages are sent to the message handler via the <a href="qabstractmessagehandler.html#message">message</a>() function, which forwards them to your handleMessge().</p>
<p>A single instance of <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a> can be called on to handle messages from multiple sources. Hence, the content of a message, which is the <i>description</i> parameter passed to <a href="qabstractmessagehandler.html#message">message</a>() and <a href="qabstractmessagehandler.html#handleMessage">handleMessage</a>(), must be interpreted in light of the context that required the message to be sent. That context is specified by the <i>identifier</i> and <i>sourceLocation</i> parameters to <a href="qabstractmessagehandler.html#message">message</a>() <a href="qabstractmessagehandler.html#handleMessage">handleMessage</a>().</p>
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<h2>Member Function Documentation</h2>
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<h3 class="fn" id="QAbstractMessageHandler"><a name="QAbstractMessageHandler"></a>QAbstractMessageHandler::<span class="name">QAbstractMessageHandler</span>(<span class="type">QObject</span> *<i>parent</i> = Q_NULLPTR)</h3>
<p>Constructs a <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a>. The <i>parent</i> is passed to the QObject base class constructor.</p>
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<h3 class="fn" id="dtor.QAbstractMessageHandler"><a name="dtor.QAbstractMessageHandler"></a><code>[virtual] </code>QAbstractMessageHandler::<span class="name">~QAbstractMessageHandler</span>()</h3>
<p>Destructs this <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a>.</p>
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<h3 class="fn" id="handleMessage"><a name="handleMessage"></a><code>[pure virtual protected] </code><span class="type">void</span> QAbstractMessageHandler::<span class="name">handleMessage</span>(<span class="type">QtMsgType</span> <i>type</i>, const <span class="type">QString</span> &<i>description</i>, const <span class="type">QUrl</span> &<i>identifier</i>, const <span class="type"><a href="qsourcelocation.html">QSourceLocation</a></span> &<i>sourceLocation</i>)</h3>
<p>This function must be implemented by the sub-class. <a href="qabstractmessagehandler.html#message">message</a>() will call this function, passing in its parameters, <i>type</i>, <i>description</i>, <i>identifier</i> and <i>sourceLocation</i> unmodified.</p>
<p>This function can potentially be called from multiple threads. It's the reimplementation's responsibility to ensure thread safety.</p>
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<h3 class="fn" id="message"><a name="message"></a><span class="type">void</span> QAbstractMessageHandler::<span class="name">message</span>(<span class="type">QtMsgType</span> <i>type</i>, const <span class="type">QString</span> &<i>description</i>, const <span class="type">QUrl</span> &<i>identifier</i> = QUrl(), const <span class="type"><a href="qsourcelocation.html">QSourceLocation</a></span> &<i>sourceLocation</i> = QSourceLocation())</h3>
<p>Sends a message to this message handler. <i>type</i> is the kind of message being sent. <i>description</i> is the message content. The <i>identifier</i> is a URI that identifies the message and is the key to interpreting the other arguments.</p>
<p>Typically, this class is used for reporting errors, as is the case for <a href="qxmlquery.html">QXmlQuery</a>, which uses a <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a> to report compile and runtime <a href="xmlprocessing.html">XQuery</a> errors. Hence, using a QUrl as the message <i>identifier</i> is was inspired by the explanation of error handling in the XQuery language. Because the <i>identifier</i> is composed of a namespace URI and a local part, identifiers with the same local part are unique. The caller is responsible for ensuring that <i>identifier</i> is either a valid QUrl or a default constructed QUrl.</p>
<p><i>sourceLocation</i> identifies a location in a resource (i.e., file or document) where the need for reporting a message was detected.</p>
<p>This function unconditionally calls <a href="qabstractmessagehandler.html#handleMessage">handleMessage</a>(), passing all its parameters unmodified.</p>
<p><b>See also </b><a href="http://www.w3.org/TR/xquery/#errors">http://www.w3.org/TR/xquery/#errors</a>.</p>
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