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<li class="level1"><a href="#public-functions">Public Functions</a></li>
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<h1 class="title">QAbstractMessageHandler Class Reference</h1>
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<p>The QAbstractMessageHandler class provides a callback interface for handling messages. <a href="#details">More...</a></p>
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<pre class="cpp"> <span class="preprocessor">#include <QAbstractMessageHandler></span></pre><p><b>Inherits: </b><a href="qobject.html">QObject</a>.</p>
<p><b>Inherited by: </b></p>
<p><b>Note:</b> All functions in this class are <a href="threads-reentrancy.html#thread-safe">thread-safe</a>.</p>
<p>This class was introduced in Qt 4.4.</p>
<ul>
<li><a href="qabstractmessagehandler-members.html">List of all members, including inherited members</a></li>
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<a name="public-functions"></a>
<h2>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> = 0 )</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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<li class="fn">29 public functions inherited from <a href="qobject.html#public-functions">QObject</a></li>
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<h2>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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<li class="fn">8 protected functions inherited from <a href="qobject.html#protected-functions">QObject</a></li>
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<h3>Additional Inherited Members</h3>
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<li class="fn">1 property inherited from <a href="qobject.html#properties">QObject</a></li>
<li class="fn">1 public slot inherited from <a href="qobject.html#public-slots">QObject</a></li>
<li class="fn">1 signal inherited from <a href="qobject.html#signals">QObject</a></li>
<li class="fn">7 static public members inherited from <a href="qobject.html#static-public-members">QObject</a></li>
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<a name="details"></a>
<!-- $$$QAbstractMessageHandler-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QAbstractMessageHandler class provides a callback interface for handling messages.</p>
<p>QAbstractMessageHandler 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 QAbstractMessageHandler. See <a href="qxmlquery.html#setMessageHandler">QXmlQuery::setMessageHandler</a>().</p>
<p>You create a message handler by subclassing QAbstractMessageHandler 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(). The effect is to serialize the handling of all messages, which means your QAbstractMessageHandler subclass is thread safe.</p>
<p>A single instance of QAbstractMessageHandler 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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<!-- @@@QAbstractMessageHandler -->
<div class="func">
<h2>Member Function Documentation</h2>
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<h3 class="fn"><a name="QAbstractMessageHandler"></a>QAbstractMessageHandler::<span class="name">QAbstractMessageHandler</span> ( <span class="type"><a href="qobject.html">QObject</a></span> * <i>parent</i> = 0 )</h3>
<p>Constructs a <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a>. The <i>parent</i> is passed to the <a href="qobject.html">QObject</a> base class constructor.</p>
<!-- @@@QAbstractMessageHandler -->
<!-- $$$~QAbstractMessageHandler[overload1]$$$~QAbstractMessageHandler -->
<h3 class="fn"><a name="dtor.QAbstractMessageHandler"></a>QAbstractMessageHandler::<span class="name">~QAbstractMessageHandler</span> ()<tt> [virtual]</tt></h3>
<p>Destructs this <a href="qabstractmessagehandler.html">QAbstractMessageHandler</a>.</p>
<!-- @@@~QAbstractMessageHandler -->
<!-- $$$handleMessage[overload1]$$$handleMessageQtMsgTypeconstQString&constQUrl&constQSourceLocation& -->
<h3 class="fn"><a name="handleMessage"></a><span class="type">void</span> QAbstractMessageHandler::<span class="name">handleMessage</span> ( <span class="type"><a href="qtglobal.html#QtMsgType-enum">QtMsgType</a></span> <i>type</i>, const <span class="type"><a href="qstring.html">QString</a></span> & <i>description</i>, const <span class="type"><a href="qurl.html">QUrl</a></span> & <i>identifier</i>, const <span class="type"><a href="qsourcelocation.html">QSourceLocation</a></span> & <i>sourceLocation</i> )<tt> [pure virtual protected]</tt></h3>
<p>This function must be implemented by the sub-class. <a href="qabstractmessagehandler.html#message">message</a>() will call this function, passing in its parameters, <i>type</i>, <i>description</i>, <i>identifier</i> and <i>sourceLocation</i> unmodified.</p>
<!-- @@@handleMessage -->
<!-- $$$message[overload1]$$$messageQtMsgTypeconstQString&constQUrl&constQSourceLocation& -->
<h3 class="fn"><a name="message"></a><span class="type">void</span> QAbstractMessageHandler::<span class="name">message</span> ( <span class="type"><a href="qtglobal.html#QtMsgType-enum">QtMsgType</a></span> <i>type</i>, const <span class="type"><a href="qstring.html">QString</a></span> & <i>description</i>, const <span class="type"><a href="qurl.html">QUrl</a></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 <a href="qurl.html">QUrl</a> as the message <i>identifier</i> is was inspired by the explanation of <a href="http://www.w3.org/TR/xquery/#errors">error handling in the XQuery language</a>. 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 <a href="qurl.html">QUrl</a> or a default constructed <a href="qurl.html">QUrl</a>.</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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