<?xml version="1.0" encoding="iso-8859-1"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <!-- /tmp/qt-4.3.4-qt-1203442408707/qt-x11-opensource-src-4.3.4/doc/src/object.qdoc --> <head> <title>Qt 4.3: Qt Object Model</title> <link href="classic.css" rel="stylesheet" type="text/css" /> </head> <body> <table border="0" cellpadding="0" cellspacing="0" width="100%"> <tr> <td align="left" valign="top" width="32"><a href="http://www.trolltech.com/products/qt"><img src="images/qt-logo.png" align="left" width="32" height="32" border="0" /></a></td> <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="mainclasses.html"><font color="#004faf">Main Classes</font></a> · <a href="groups.html"><font color="#004faf">Grouped Classes</font></a> · <a href="modules.html"><font color="#004faf">Modules</font></a> · <a href="functions.html"><font color="#004faf">Functions</font></a></td> <td align="right" valign="top" width="230"><a href="http://www.trolltech.com"><img src="images/trolltech-logo.png" align="right" width="203" height="32" border="0" /></a></td></tr></table><h1 align="center">Qt Object Model<br /><small></small></h1> <p>The standard C++ object model provides very efficient runtime support for the object paradigm. But its static nature is inflexibile in certain problem domains. Graphical user interface programming is a domain that requires both runtime efficiency and a high level of flexibility. Qt provides this, by combining the speed of C++ with the flexibility of the Qt Object Model.</p> <p>Qt adds these features to C++:</p> <ul> <li>a very powerful mechanism for seamless object communication called <a href="signalsandslots.html">signals and slots</a></li> <li>queryable and designable <a href="properties.html">object properties</a></li> <li>powerful <a href="eventsandfilters.html">events and event filters</a></li> <li>contextual <a href="i18n.html">string translation for internationalization</a></li> <li>sophisticated interval driven <a href="timers.html">timers</a> that make it possible to elegantly integrate many tasks in an event-driven GUI</li> <li>hierarchical and queryable <a href="objecttrees.html">object trees</a> that organize object ownership in a natural way</li> <li>guarded pointers (<a href="qpointer.html">QPointer</a>) that are automatically set to 0 when the referenced object is destroyed, unlike normal C++ pointers which become dangling pointers when their objects are destroyed</li> <li>a <a href="metaobjects.html#qobjectcast">dynamic cast</a> that works across library boundaries.</li> </ul> <p>Many of these Qt features are implemented with standard C++ techniques, based on inheritance from <a href="qobject.html">QObject</a>. Others, like the object communication mechanism and the dynamic property system, require the <a href="metaobjects.html">Meta-Object System</a> provided by Qt's own <a href="moc.html#moc">Meta-Object Compiler (moc)</a>.</p> <p>The meta-object system is a C++ extension that makes the language better suited to true component GUI programming. Although templates can be used to extend C++, the meta-object system provides benefits using standard C++ that cannot be achieved with templates; see <a href="templates.html">Why Doesn't Qt Use Templates for Signals and Slots?</a></p> <p /><address><hr /><div align="center"> <table width="100%" cellspacing="0" border="0"><tr class="address"> <td width="30%">Copyright © 2008 <a href="trolltech.html">Trolltech</a></td> <td width="40%" align="center"><a href="trademarks.html">Trademarks</a></td> <td width="30%" align="right"><div align="right">Qt 4.3.4</div></td> </tr></table></div></address></body> </html>