Files
qt4-x11/doc/html/qdbustypesystem.html
2025-08-24 20:55:26 +08:00

258 lines
14 KiB
HTML

<?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">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en_US" lang="en_US">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<!-- dbus-adaptors.qdoc -->
<title>Qt 4.8: The QtDBus Type System</title>
<link rel="stylesheet" type="text/css" href="style/style.css" />
<script src="scripts/jquery.js" type="text/javascript"></script>
<script src="scripts/functions.js" type="text/javascript"></script>
<link rel="stylesheet" type="text/css" href="style/superfish.css" />
<link rel="stylesheet" type="text/css" href="style/narrow.css" />
<!--[if IE]>
<meta name="MSSmartTagsPreventParsing" content="true">
<meta http-equiv="imagetoolbar" content="no">
<![endif]-->
<!--[if lt IE 7]>
<link rel="stylesheet" type="text/css" href="style/style_ie6.css">
<![endif]-->
<!--[if IE 7]>
<link rel="stylesheet" type="text/css" href="style/style_ie7.css">
<![endif]-->
<!--[if IE 8]>
<link rel="stylesheet" type="text/css" href="style/style_ie8.css">
<![endif]-->
<script src="scripts/superfish.js" type="text/javascript"></script>
<script src="scripts/narrow.js" type="text/javascript"></script>
</head>
<body class="" onload="CheckEmptyAndLoadList();">
<div class="header" id="qtdocheader">
<div class="content">
<div id="nav-logo">
<a href="index.html">Home</a></div>
<a href="index.html" class="qtref"><span>Qt Reference Documentation</span></a>
<div id="narrowsearch"></div>
<div id="nav-topright">
<ul>
<li class="nav-topright-home"><a href="http://qt.digia.com/">Qt HOME</a></li>
<li class="nav-topright-dev"><a href="http://qt-project.org/">DEV</a></li>
<li class="nav-topright-doc nav-topright-doc-active"><a href="http://qt-project.org/doc/">
DOC</a></li>
<li class="nav-topright-blog"><a href="http://blog.qt.digia.com/">BLOG</a></li>
</ul>
</div>
<div id="shortCut">
<ul>
<li class="shortCut-topleft-inactive"><span><a href="index.html">Qt 4.8</a></span></li>
<li class="shortCut-topleft-active"><a href="http://qt-project.org/doc/">ALL VERSIONS </a></li>
</ul>
</div>
<ul class="sf-menu" id="narrowmenu">
<li><a href="#">API Lookup</a>
<ul>
<li><a href="classes.html">Class index</a></li>
<li><a href="functions.html">Function index</a></li>
<li><a href="modules.html">Modules</a></li>
<li><a href="namespaces.html">Namespaces</a></li>
<li><a href="qtglobal.html">Global Declarations</a></li>
<li><a href="qdeclarativeelements.html">QML elements</a></li>
</ul>
</li>
<li><a href="#">Qt Topics</a>
<ul>
<li><a href="qt-basic-concepts.html">Programming with Qt</a></li>
<li><a href="qtquick.html">Device UIs &amp; Qt Quick</a></li>
<li><a href="qt-gui-concepts.html">UI Design with Qt</a></li>
<li><a href="supported-platforms.html">Supported Platforms</a></li>
<li><a href="technology-apis.html">Qt and Key Technologies</a></li>
<li><a href="best-practices.html">How-To's and Best Practices</a></li>
</ul>
</li>
<li><a href="#">Examples</a>
<ul>
<li><a href="all-examples.html">Examples</a></li>
<li><a href="tutorials.html">Tutorials</a></li>
<li><a href="demos.html">Demos</a></li>
<li><a href="qdeclarativeexamples.html">QML Examples</a></li>
</ul>
</li>
</ul>
</div>
</div>
<div class="wrapper">
<div class="hd">
<span></span>
</div>
<div class="bd group">
<div class="sidebar">
<div class="searchlabel">
Search index:</div>
<div class="search" id="sidebarsearch">
<form id="qtdocsearch" action="" onsubmit="return false;">
<fieldset>
<input type="text" name="searchstring" id="pageType" value="" />
<div id="resultdialog">
<a href="#" id="resultclose">Close</a>
<p id="resultlinks" class="all"><a href="#" id="showallresults">All</a> | <a href="#" id="showapiresults">API</a> | <a href="#" id="showarticleresults">Articles</a> | <a href="#" id="showexampleresults">Examples</a></p>
<p id="searchcount" class="all"><span id="resultcount"></span><span id="apicount"></span><span id="articlecount"></span><span id="examplecount"></span>&nbsp;results:</p>
<ul id="resultlist" class="all">
</ul>
</div>
</fieldset>
</form>
</div>
<div class="box first bottombar" id="lookup">
<h2 title="API Lookup"><span></span>
API Lookup</h2>
<div id="list001" class="list">
<ul id="ul001" >
<li class="defaultLink"><a href="classes.html">Class index</a></li>
<li class="defaultLink"><a href="functions.html">Function index</a></li>
<li class="defaultLink"><a href="modules.html">Modules</a></li>
<li class="defaultLink"><a href="namespaces.html">Namespaces</a></li>
<li class="defaultLink"><a href="qtglobal.html">Global Declarations</a></li>
<li class="defaultLink"><a href="qdeclarativeelements.html">QML elements</a></li>
</ul>
</div>
</div>
<div class="box bottombar" id="topics">
<h2 title="Qt Topics"><span></span>
Qt Topics</h2>
<div id="list002" class="list">
<ul id="ul002" >
<li class="defaultLink"><a href="qt-basic-concepts.html">Programming with Qt</a></li>
<li class="defaultLink"><a href="qtquick.html">Device UIs &amp; Qt Quick</a></li>
<li class="defaultLink"><a href="qt-gui-concepts.html">UI Design with Qt</a></li>
<li class="defaultLink"><a href="supported-platforms.html">Supported Platforms</a></li>
<li class="defaultLink"><a href="technology-apis.html">Qt and Key Technologies</a></li>
<li class="defaultLink"><a href="best-practices.html">How-To's and Best Practices</a></li>
</ul>
</div>
</div>
<div class="box" id="examples">
<h2 title="Examples"><span></span>
Examples</h2>
<div id="list003" class="list">
<ul id="ul003">
<li class="defaultLink"><a href="all-examples.html">Examples</a></li>
<li class="defaultLink"><a href="tutorials.html">Tutorials</a></li>
<li class="defaultLink"><a href="demos.html">Demos</a></li>
<li class="defaultLink"><a href="qdeclarativeexamples.html">QML Examples</a></li>
</ul>
</div>
</div>
</div>
<div class="wrap">
<div class="toolbar">
<div class="breadcrumb toolblock">
<ul>
<li class="first"><a href="index.html">Home</a></li>
<!-- Breadcrumbs go here -->
<li>The QtDBus Type System</li>
</ul>
</div>
<div class="toolbuttons toolblock">
<ul>
<li id="smallA" class="t_button">A</li>
<li id="medA" class="t_button active">A</li>
<li id="bigA" class="t_button">A</li>
<li id="print" class="t_button"><a href="javascript:this.print();">
<span>Print</span></a></li>
</ul>
</div>
</div>
<div class="content mainContent">
<link rel="prev" href="qdbusdeclaringsignals.html" />
<link rel="next" href="qdbusadaptorexample.html" />
<p class="naviNextPrevious headerNavi">
<a class="prevPage" href="qdbusdeclaringsignals.html">Declaring Signals in D-Bus Adaptors</a>
<a class="nextPage" href="qdbusadaptorexample.html">D-Bus Adaptor Example</a>
</p><p/>
<div class="toc">
<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#primitive-types">Primitive Types</a></li>
<li class="level1"><a href="#compound-types">Compound Types</a></li>
<li class="level1"><a href="#extending-the-type-system">Extending the Type System</a></li>
<li class="level1"><a href="#the-type-system-in-use">The Type System in Use</a></li>
</ul>
</div>
<h1 class="title">The QtDBus Type System</h1>
<span class="subtitle"></span>
<!-- $$$qdbustypesystem.html-description -->
<div class="descr"> <a name="details"></a>
<p>D-Bus has an extensible type system based on a few primitives and composition of the primitives in arrays and structures. <a href="qtdbus.html">QtDBus</a> implements the interface to that type system through the <a href="qdbusargument.html">QDBusArgument</a> class, allowing user programs to send and receive practically every C++ type over the bus.</p>
<a name="primitive-types"></a>
<h2>Primitive Types</h2>
<p>The primitive types are supported natively by <a href="qdbusargument.html">QDBusArgument</a> and need no special customization to be sent or received. They are listed below, along with the C++ class they relate to:</p>
<table class="generic">
<thead><tr class="qt-style"><th >Qt type</th><th >D-Bus equivalent type</th></tr></thead>
<tr valign="top" class="odd"><td >uchar</td><td >BYTE</td></tr>
<tr valign="top" class="even"><td >bool</td><td >BOOLEAN</td></tr>
<tr valign="top" class="odd"><td >short</td><td >INT16</td></tr>
<tr valign="top" class="even"><td >ushort</td><td >UINT16</td></tr>
<tr valign="top" class="odd"><td >int</td><td >INT32</td></tr>
<tr valign="top" class="even"><td >uint</td><td >UINT32</td></tr>
<tr valign="top" class="odd"><td >qlonglong</td><td >INT64</td></tr>
<tr valign="top" class="even"><td >qulonglong</td><td >UINT64</td></tr>
<tr valign="top" class="odd"><td >double</td><td >DOUBLE</td></tr>
<tr valign="top" class="even"><td ><a href="qstring.html">QString</a></td><td >STRING</td></tr>
<tr valign="top" class="odd"><td ><a href="qdbusvariant.html">QDBusVariant</a></td><td >VARIANT</td></tr>
<tr valign="top" class="even"><td ><a href="qdbusobjectpath.html">QDBusObjectPath</a></td><td ><a href="intro-to-dbus.html#object-paths">OBJECT_PATH</a></td></tr>
<tr valign="top" class="odd"><td ><a href="qdbussignature.html">QDBusSignature</a></td><td >SIGNATURE</td></tr>
</table>
<p>Aside from the primitive types, <a href="qdbusargument.html">QDBusArgument</a> also supports two non-primitive types natively, due to their widespread use in Qt applications: <a href="qstringlist.html">QStringList</a> and <a href="qbytearray.html">QByteArray</a>.</p>
<a name="compound-types"></a>
<h2>Compound Types</h2>
<p>D-Bus specifies three types of aggregations of primitive types that allow one to create compound types. They are <tt>ARRAY</tt>, <tt>STRUCT</tt> and maps/dictionaries.</p>
<p>Arrays are sets of zero or more elements of the same type, while structures are a set of a fixed number of elements, each of any type. Maps or dictionaries are implemented as arrays of a pair of elements, so there can be zero or more elements in one map.</p>
<a name="extending-the-type-system"></a>
<h2>Extending the Type System</h2>
<p>In order to use one's own type with <a href="qtdbus.html">QtDBus</a>, the type has to be declared as a Qt meta-type with the <a href="qmetatype.html#Q_DECLARE_METATYPE">Q_DECLARE_METATYPE</a>() macro and registered with the <a href="qdbusargument.html#qDBusRegisterMetaType">qDBusRegisterMetaType</a>() function. The streaming operators <tt>operator&gt;&gt;</tt> and <tt>operator&lt;&lt;</tt> will be automatically found by the registration system.</p>
<p><a href="qtdbus.html">QtDBus</a> provides template specializations for arrays and maps for use with Qt's <a href="containers.html">container classes</a>, such as <a href="qmap.html">QMap</a> and <a href="qlist.html">QList</a>, so it is not necessary to write the streaming operator functions for those. For other types, and specially for types implementing structures, the operators have to be explicitly implemented.</p>
<p>See the documentation for <a href="qdbusargument.html">QDBusArgument</a> for examples for structures, arrays and maps.</p>
<a name="the-type-system-in-use"></a>
<h2>The Type System in Use</h2>
<p>All of the <a href="qtdbus.html">QtDBus</a> types (primitives and user-defined alike) can be used to send and receive messages of all types over the bus.</p>
<p><b>Warning:</b> You may not use any type that is not on the list above, including <i>typedefs</i> to the types listed. This also includes <a href="qlist.html">QList</a>&lt;<a href="qvariant.html">QVariant</a>&gt; and <a href="qmap.html">QMap</a>&lt;<a href="qstring.html">QString</a>,<a href="qvariant.html">QVariant</a>&gt;.</p>
</div>
<!-- @@@qdbustypesystem.html -->
<p class="naviNextPrevious footerNavi">
<a class="prevPage" href="qdbusdeclaringsignals.html">Declaring Signals in D-Bus Adaptors</a>
<a class="nextPage" href="qdbusadaptorexample.html">D-Bus Adaptor Example</a>
</p>
</div>
</div>
</div>
<div class="ft">
<span></span>
</div>
</div>
<div class="footer">
<p>
<acronym title="Copyright">&copy;</acronym> 2015 The Qt Company Ltd.
Documentation contributions included herein are the copyrights of
their respective owners.</p>
<br />
<p>
The documentation provided herein is licensed under the terms of the
<a href="http://www.gnu.org/licenses/fdl.html">GNU Free Documentation
License version 1.3</a> as published by the Free Software Foundation.</p>
<p>
Documentation sources may be obtained from <a href="http://www.qt-project.org">
www.qt-project.org</a>.</p>
<br />
<p>
Qt and respective logos are trademarks of The Qt Company Ltd
in Finland and/or other countries worldwide. All other trademarks are property
of their respective owners. <a title="Privacy Policy"
href="http://en.gitorious.org/privacy_policy/">Privacy Policy</a></p>
</div>
<script src="scripts/functions.js" type="text/javascript"></script>
</body>
</html>