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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<!-- qdbuscontext.cpp -->
  <title>Qt 4.8: QDBusContext Class Reference</title>
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  <div class="content"> 
    <a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
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<li><a href="modules.html">Modules</a></li>
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<div class="content mainContent">
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#public-functions">Public Functions</a></li>
<li class="level1"><a href="#details">Detailed Description</a></li>
</ul>
</div>
<h1 class="title">QDBusContext Class Reference</h1>
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<p>The QDBusContext class allows slots to determine the D-Bus context of the calls. <a href="#details">More...</a></p>
<!-- @@@QDBusContext -->
<pre class="cpp"> <span class="preprocessor">#include &lt;QDBusContext&gt;</span></pre><p>This class was introduced in Qt 4.3.</p>
<ul>
<li><a href="qdbuscontext-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="public-functions"></a>
<h2>Public Functions</h2>
<table class="alignedsummary">
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#QDBusContext">QDBusContext</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#dtor.QDBusContext">~QDBusContext</a></b> ()</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#calledFromDBus">calledFromDBus</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> QDBusConnection </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#connection">connection</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> bool </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#isDelayedReply">isDelayedReply</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> const QDBusMessage &amp; </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#message">message</a></b> () const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#sendErrorReply">sendErrorReply</a></b> ( const QString &amp; <i>name</i>, const QString &amp; <i>msg</i> = QString() ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#sendErrorReply-2">sendErrorReply</a></b> ( QDBusError::ErrorType <i>type</i>, const QString &amp; <i>msg</i> = QString() ) const</td></tr>
<tr><td class="memItemLeft rightAlign topAlign"> void </td><td class="memItemRight bottomAlign"><b><a href="qdbuscontext.html#setDelayedReply">setDelayedReply</a></b> ( bool <i>enable</i> ) const</td></tr>
</table>
<a name="details"></a>
<!-- $$$QDBusContext-description -->
<div class="descr">
<h2>Detailed Description</h2>
<p>The QDBusContext class allows slots to determine the D-Bus context of the calls.</p>
<p>When a slot is called in an object due to a signal delivery or due to a remote method call, it is sometimes necessary to know the context in which that happened. In particular, if the slot determines that it wants to send the reply at a later opportunity or if it wants to reply with an error, the context is needed.</p>
<p>The QDBusContext class is an alternative to accessing the context that doesn't involve modifying the code generated by the <a href="qdbusxml2cpp.html">QtDBus XML Compiler (qdbusxml2cpp)</a>.</p>
<p>QDBusContext is used by subclassing it from the objects being exported using <a href="qdbusconnection.html#registerObject">QDBusConnection::registerObject</a>(). The following example illustrates the usage:</p>
<pre class="cpp"> <span class="keyword">class</span> MyObject: <span class="keyword">public</span> <span class="type"><a href="qobject.html">QObject</a></span><span class="operator">,</span>
                 <span class="keyword">protected</span> <span class="type">QDBusContext</span>
 {
     Q_OBJECT
     <span class="type"><a href="qdbusconnection.html">QDBusConnection</a></span> conn;
     <span class="type"><a href="qdbusmessage.html">QDBusMessage</a></span> msg;

 <span class="operator">.</span><span class="operator">.</span><span class="operator">.</span>

 <span class="keyword">protected</span> <span class="keyword">slots</span>:
     <span class="type">void</span> process();
 <span class="keyword">public</span> <span class="keyword">slots</span>:
     <span class="type">void</span> methodWithError();
     <span class="type"><a href="qstring.html">QString</a></span> methodWithDelayedReply();
 };

 <span class="type">void</span> MyObject<span class="operator">::</span>methodWithError()
 {
     sendErrorReply(<span class="type"><a href="qdbuserror.html">QDBusError</a></span><span class="operator">::</span>NotSupported<span class="operator">,</span>
                    <span class="string">&quot;The method call 'methodWithError()' is not supported&quot;</span>);
 }

 <span class="type"><a href="qstring.html">QString</a></span> MyObject<span class="operator">::</span>methodWithDelayedReply()
 {
     conn <span class="operator">=</span> connection();
     msg <span class="operator">=</span> message();
     setDelayedReply(<span class="keyword">true</span>);
     <span class="type"><a href="qmetaobject.html">QMetaObject</a></span><span class="operator">::</span>invokeMethod(<span class="keyword">this</span><span class="operator">,</span> <span class="string">&quot;process&quot;</span><span class="operator">,</span> <span class="type"><a href="qt.html">Qt</a></span><span class="operator">::</span>QueuedConnection);
     <span class="keyword">return</span> <span class="type"><a href="qstring.html">QString</a></span>();
 }</pre>
<p>The example illustrates the two typical uses, that of sending error replies and that of delayed replies.</p>
<p>Note: do not subclass QDBusContext and <a href="qdbusabstractadaptor.html">QDBusAbstractAdaptor</a> at the same time. QDBusContext should appear in the real object, not the adaptor. If it's necessary from the adaptor code to determine the context, use a public inheritance and access the functions via <a href="qobject.html#parent">QObject::parent</a>().</p>
</div>
<!-- @@@QDBusContext -->
<div class="func">
<h2>Member Function Documentation</h2>
<!-- $$$QDBusContext[overload1]$$$QDBusContext -->
<h3 class="fn"><a name="QDBusContext"></a>QDBusContext::<span class="name">QDBusContext</span> ()</h3>
<p>Constructs an empty <a href="qdbuscontext.html">QDBusContext</a>.</p>
<!-- @@@QDBusContext -->
<!-- $$$~QDBusContext[overload1]$$$~QDBusContext -->
<h3 class="fn"><a name="dtor.QDBusContext"></a>QDBusContext::<span class="name">~QDBusContext</span> ()</h3>
<p>An empty destructor.</p>
<!-- @@@~QDBusContext -->
<!-- $$$calledFromDBus[overload1]$$$calledFromDBus -->
<h3 class="fn"><a name="calledFromDBus"></a><span class="type">bool</span> QDBusContext::<span class="name">calledFromDBus</span> () const</h3>
<p>Returns true if we are processing a D-Bus call. If this function returns true, the rest of the functions in this class are available.</p>
<p>Accessing those functions when this function returns false is undefined and may lead to crashes.</p>
<!-- @@@calledFromDBus -->
<!-- $$$connection[overload1]$$$connection -->
<h3 class="fn"><a name="connection"></a><span class="type"><a href="qdbusconnection.html">QDBusConnection</a></span> QDBusContext::<span class="name">connection</span> () const</h3>
<p>Returns the connection from which this call was received.</p>
<!-- @@@connection -->
<!-- $$$isDelayedReply[overload1]$$$isDelayedReply -->
<h3 class="fn"><a name="isDelayedReply"></a><span class="type">bool</span> QDBusContext::<span class="name">isDelayedReply</span> () const</h3>
<p>Returns true if this call will have a delayed reply.</p>
<p><b>See also </b><a href="qdbuscontext.html#setDelayedReply">setDelayedReply</a>().</p>
<!-- @@@isDelayedReply -->
<!-- $$$message[overload1]$$$message -->
<h3 class="fn"><a name="message"></a>const <span class="type"><a href="qdbusmessage.html">QDBusMessage</a></span> &amp; QDBusContext::<span class="name">message</span> () const</h3>
<p>Returns the message that generated this call.</p>
<!-- @@@message -->
<!-- $$$sendErrorReply[overload1]$$$sendErrorReplyconstQString&constQString& -->
<h3 class="fn"><a name="sendErrorReply"></a><span class="type">void</span> QDBusContext::<span class="name">sendErrorReply</span> ( const <span class="type"><a href="qstring.html">QString</a></span> &amp; <i>name</i>, const <span class="type"><a href="qstring.html">QString</a></span> &amp; <i>msg</i> = QString() ) const</h3>
<p>Sends an error <i>name</i> as a reply to the caller. The optional <i>msg</i> parameter is a human-readable text explaining the failure.</p>
<p>If an error is sent, the return value and any output parameters from the called slot will be ignored by <a href="qtdbus.html">QtDBus</a>.</p>
<!-- @@@sendErrorReply -->
<!-- $$$sendErrorReply$$$sendErrorReplyQDBusError::ErrorTypeconstQString& -->
<h3 class="fn"><a name="sendErrorReply-2"></a><span class="type">void</span> QDBusContext::<span class="name">sendErrorReply</span> ( <span class="type"><a href="qdbuserror.html#ErrorType-enum">QDBusError::ErrorType</a></span> <i>type</i>, const <span class="type"><a href="qstring.html">QString</a></span> &amp; <i>msg</i> = QString() ) const</h3>
<p>This is an overloaded function.</p>
<p>Sends an error <i>type</i> as a reply to the caller. The optional <i>msg</i> parameter is a human-readable text explaining the failure.</p>
<p>If an error is sent, the return value and any output parameters from the called slot will be ignored by <a href="qtdbus.html">QtDBus</a>.</p>
<!-- @@@sendErrorReply -->
<!-- $$$setDelayedReply[overload1]$$$setDelayedReplybool -->
<h3 class="fn"><a name="setDelayedReply"></a><span class="type">void</span> QDBusContext::<span class="name">setDelayedReply</span> ( <span class="type">bool</span> <i>enable</i> ) const</h3>
<p>Sets whether this call will have a delayed reply or not.</p>
<p>If <i>enable</i> is false, <a href="qtdbus.html">QtDBus</a> will automatically generate a reply back to the caller, if needed, as soon as the called slot returns.</p>
<p>If <i>enable</i> is true, <a href="qtdbus.html">QtDBus</a> will not generate automatic replies. It will also ignore the return value from the slot and any output parameters. Instead, the called object is responsible for storing the incoming message and send a reply or error at a later time.</p>
<p>Failing to send a reply will result in an automatic timeout error being generated by D-Bus.</p>
<p><b>See also </b><a href="qdbuscontext.html#isDelayedReply">isDelayedReply</a>().</p>
<!-- @@@setDelayedReply -->
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