source: trunk/src/kernel/qobjectcleanuphandler.cpp@ 95

/****************************************************************************
** $Id: qobjectcleanuphandler.cpp 2 2005-11-16 15:49:26Z dmik $
**
** Implementation of QObjectCleanupHandler class
**
** Copyright (C) 2000-2001 Trolltech AS.  All rights reserved.
**
** This file is part of the kernel module of the Qt GUI Toolkit.
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** as defined by Trolltech AS of Norway and appearing in the file
** LICENSE.QPL included in the packaging of this file.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
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** licenses may use this file in accordance with the Qt Commercial License
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#include "qobjectcleanuphandler.h"
#include "qobjectlist.h"

/*!
    \class QObjectCleanupHandler qobjectcleanuphandler.h
    \brief The QObjectCleanupHandler class watches the lifetime of multiple QObjects.

    \ingroup objectmodel

    A QObjectCleanupHandler is useful whenever you need to know when a
    number of \l{QObject}s that are owned by someone else have been
    deleted. This is important, for example, when referencing memory
    in an application that has been allocated in a shared library.

    Example:

    \code
    class FactoryComponent : public FactoryInterface, public QLibraryInterface
    {
    public:
        ...

        QObject *createObject();

        bool init();
        void cleanup();
        bool canUnload() const;

    private:
        QObjectCleanupHandler objects;
    };

    // allocate a new object, and add it to the cleanup handler
    QObject *FactoryComponent::createObject()
    {
        return objects.add( new QObject() );
    }

    // QLibraryInterface implementation
    bool FactoryComponent::init()
    {
        return TRUE;
    }

    void FactoryComponent::cleanup()
    {
    }

    // it is only safe to unload the library when all QObject's have been destroyed
    bool FactoryComponent::canUnload() const
    {
        return objects.isEmpty();
    }
    \endcode
*/

/*!
    Constructs an empty QObjectCleanupHandler.
*/
QObjectCleanupHandler::QObjectCleanupHandler()
: QObject(), cleanupObjects( 0 )
{
}

/*!
    Destroys the cleanup handler. All objects in this cleanup handler
    will be deleted.
*/
QObjectCleanupHandler::~QObjectCleanupHandler()
{
    clear();
}

/*!
    Adds \a object to this cleanup handler and returns the pointer to
    the object.
*/
QObject* QObjectCleanupHandler::add( QObject* object )
{
    if ( !object )
        return 0;

    if ( !cleanupObjects ) {
        cleanupObjects = new QObjectList;
        cleanupObjects->setAutoDelete( TRUE );
    }
    connect( object, SIGNAL(destroyed(QObject*)), this, SLOT(objectDestroyed(QObject*)) );
    cleanupObjects->insert( 0, object );
    return object;
}

/*!
    Removes the \a object from this cleanup handler. The object will
    not be destroyed.
*/
void QObjectCleanupHandler::remove( QObject *object )
{
    if ( !cleanupObjects )
        return;
    if ( cleanupObjects->findRef( object ) >= 0 ) {
        (void) cleanupObjects->take();
        disconnect( object, SIGNAL(destroyed(QObject*)), this, SLOT(objectDestroyed(QObject*)) );
    }
}

/*!
    Returns TRUE if this cleanup handler is empty or if all objects in
    this cleanup handler have been destroyed; otherwise return FALSE.
*/
bool QObjectCleanupHandler::isEmpty() const
{
    return cleanupObjects ? cleanupObjects->isEmpty() : TRUE;
}

/*!
    Deletes all objects in this cleanup handler. The cleanup handler
    becomes empty.
*/
void QObjectCleanupHandler::clear()
{
    delete cleanupObjects;
    cleanupObjects = 0;
}

void QObjectCleanupHandler::objectDestroyed( QObject*object )
{
    if ( cleanupObjects )
        cleanupObjects->setAutoDelete( FALSE );

    remove( object );

    if ( cleanupObjects )
        cleanupObjects->setAutoDelete( TRUE );
}