<?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"> <!-- /home/gvatteka/dev/qt-4.3/doc/src/object.qdoc --> <head> <title>Qt Object Model</title> <link href="classic.css" rel="stylesheet" type="text/css" /> </head> <body> <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="qtjambi-signalsandslots.html">signals and slots</tt></a></li> <li>queryable and designable <a href="properties.html">object properties</tt></a></li> <li>powerful <a href="eventsandfilters.html">events and event filters</tt></a></li> <li>contextual string translation for internationalization</tt></li> <li>sophisticated interval driven <a href="timers.html">timers</tt></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</tt></a> that organize object ownership in a natural way</li> <li>guarded pointers (QPointer) 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</tt></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="core/QObject.html"><tt>QObject</tt></a>. Others, like the object communication mechanism and the dynamic property system, require the <a href="metaobjects.html">Meta-Object System</tt></a> provided by Qt's own <a href="moc.html#moc">Meta-Object Compiler (moc)</tt></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?</tt></a></p> <p /><address><hr /><div align="center"> <table width="100%" cellspacing="0" border="0"><tr class="address"> <td width="30%">Copyright © 2007 <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 Jambi </div></td> </tr></table></div></address></body> </html>