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94 lines
4.3 KiB
94 lines
4.3 KiB
13 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/metaobjects.doc:36 -->
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>Meta Object System</title>
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<font color="#004faf">Home</font></a>
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<font color="#004faf">All Classes</font></a>
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<font color="#004faf">Main Classes</font></a>
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<font color="#004faf">Functions</font></a>
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</td>
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<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Meta Object System</h1>
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<p> <!-- index meta object --><a name="meta-object"></a><!-- index Q_OBJECT --><a name="Q_OBJECT"></a>
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<p> TQt's Meta Object System provides the signals and slots mechanism for
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inter-object communication, runtime type information, and the dynamic
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property system.
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<p> The Meta Object System is based on three things:
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<ol type=1>
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<li> the <a href="qobject.html">TQObject</a> class;
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<li> the Q_OBJECT macro inside the private section of the class
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declaration;
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<li> the <a href="moc.html">Meta Object Compiler (moc)</a>.
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</ol>
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<p> The <em><a href="moc.html#moc">moc</a></em> reads a C++ source file. If it finds one or more class
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declarations that contain the Q_OBJECT macro, it produces another C++
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source file which contains the meta object code for the classes that
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contain the Q_OBJECT macro. This generated source file is either
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#included into the class's source file or compiled and linked with the
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class's implementation.
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<p> In addition to providing the <a href="signalsandslots.html">signals and
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slots</a> mechanism for communication between objects (the main
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reason for introducing the system), the meta object code provides
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additional features in TQObject:
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<p> <ul>
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<p> <li> the <a href="qobject.html#className">className()</a> function that
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returns the class name as a string at runtime, without retquiring
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native runtime type information (RTTI) support through the C++
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compiler.
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<p> <li> the <a href="qobject.html#inherits">inherits()</a> function that
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returns whether an object is an instance of a class that inherits a
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specified class within the <a href="qobject.html">TQObject</a> inheritance tree.
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<p> <li> the <a href="qobject.html#tr">tr()</a> and
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<a href="qobject.html#trUtf8">trUtf8()</a> functions for string
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translation as used for <a href="i18n.html#internationalization">internationalization</a>.
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<p> <li> the <a href="qobject.html#setProperty">setProperty()</a> and <a href="qobject.html#property">property()</a> functions for dynamically
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setting and getting <a href="properties.html">object properties</a> by
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name.
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<p> <li> the <a href="qobject.html#metaObject">metaObject()</a> function that
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returns the associated <a href="qmetaobject.html">meta object</a> for the
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class.
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<p> </ul>
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<p> While it is possible to use TQObject as a base class without the
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Q_OBJECT macro and without meta object code, neither signals and slots
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nor the other features described here will be available if the
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Q_OBJECT macro is not used. From the meta object system's point of
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view, a TQObject subclass without meta code is equivalent to its
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closest ancestor with meta object code. This means for example, that
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className() will not return the actual name of your class, but the
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class name of this ancestor. We <em>strongly</em> recommend that all
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subclasses of <a href="qobject.html">TQObject</a> use the Q_OBJECT macro regardless of whether
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they actually use signals, slots and properties or not.
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<p>
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<!-- eof -->
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>TQt 3.3.8</div>
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</table></div></address></body>
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</html>
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