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109 lines
4.3 KiB
109 lines
4.3 KiB
14 years ago
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/****************************************************************************
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**
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** Explanation of moc and the meta object system
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**
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** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
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**
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** This file is part of the Qt GUI Toolkit.
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**
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** This file may be used under the terms of the GNU General
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** Public License versions 2.0 or 3.0 as published by the Free
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** Software Foundation and appearing in the files LICENSE.GPL2
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** and LICENSE.GPL3 included in the packaging of this file.
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** Alternatively you may (at your option) use any later version
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** of the GNU General Public License if such license has been
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** publicly approved by Trolltech ASA (or its successors, if any)
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** and the KDE Free Qt Foundation.
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**
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** Please review the following information to ensure GNU General
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** Public Licensing requirements will be met:
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** http://trolltech.com/products/qt/licenses/licensing/opensource/.
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** If you are unsure which license is appropriate for your use, please
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** review the following information:
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** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
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** or contact the sales department at sales@trolltech.com.
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**
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** This file may be used under the terms of the Q Public License as
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** defined by Trolltech ASA and appearing in the file LICENSE.QPL
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** included in the packaging of this file. Licensees holding valid Qt
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** Commercial licenses may use this file in accordance with the Qt
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** Commercial License Agreement provided with the Software.
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**
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** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
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** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
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** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
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** herein.
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**
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**********************************************************************/
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/*!
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\page metaobjects.html
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\title Meta Object System
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\keyword meta object
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\keyword Q_OBJECT
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Qt'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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The Meta Object System is based on three things:
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\list 1
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\i the \l QObject class;
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\i the Q_OBJECT macro inside the private section of the class
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declaration;
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\i the \link moc.html Meta Object Compiler (moc)\endlink.
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\endlist
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The \e moc 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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In addition to providing the \link signalsandslots.html signals and
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slots \endlink 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 QObject:
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\list
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\i the \link QObject::className() className() \endlink function that
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returns the class name as a string at runtime, without requiring
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native runtime type information (RTTI) support through the C++
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compiler.
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\i the \link QObject::inherits() inherits() \endlink 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 QObject inheritance tree.
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\i the \link QObject::tr() tr() \endlink and
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\link QObject::trUtf8() trUtf8() \endlink functions for string
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translation as used for internationalization.
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\i the \link QObject::setProperty() setProperty() \endlink and \link
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QObject::property() property() \endlink functions for dynamically
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setting and getting \link properties.html object properties\endlink by
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name.
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\i the \link QObject::metaObject() metaObject() \endlink function that
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returns the associated \link QMetaObject meta object \endlink for the
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class.
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\endlist
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While it is possible to use QObject 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 QObject 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 \e strongly recommend that all
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subclasses of QObject 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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*/
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