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227 lines
7.0 KiB
227 lines
7.0 KiB
/****************************************************************************
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**
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** Implementation of TQGuardedPtr class
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**
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** Created : 990929
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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 kernel module of the TQt 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 TQt 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.TQPL
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** included in the packaging of this file. Licensees holding valid TQt
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** Commercial licenses may use this file in accordance with the TQt
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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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#include "ntqguardedptr.h"
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/*!
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\class TQGuardedPtr ntqguardedptr.h
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\brief The TQGuardedPtr class is a template class that provides guarded pointers to TQObjects.
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\ingroup objectmodel
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\mainclass
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A guarded pointer, \c{TQGuardedPtr<X>}, behaves like a normal C++
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pointer \c{X*}, except that it is automatically set to 0 when
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the referenced object is destroyed (unlike normal C++ pointers,
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which become "dangling pointers" in such cases). \c X must be a
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subclass of TQObject.
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Guarded pointers are useful whenever you need to store a pointer
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to a TQObject that is owned by someone else and therefore might be
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destroyed while you still hold a reference to it. You can safely
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test the pointer for validity.
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Example:
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\code
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TQGuardedPtr<TQLabel> label = new TQLabel( 0, "label" );
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label->setText( "I like guarded pointers" );
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delete (TQLabel*) label; // simulate somebody destroying the label
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if ( label)
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label->show();
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else
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tqDebug("The label has been destroyed");
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\endcode
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The program will output \c{The label has been destroyed} rather
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than dereferencing an invalid address in \c label->show().
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The functions and operators available with a TQGuardedPtr are the
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same as those available with a normal unguarded pointer, except
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the pointer arithmetic operators (++, --, -, and +), which are
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normally used only with arrays of objects. Use them like normal
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pointers and you will not need to read this class documentation.
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For creating guarded pointers, you can construct or assign to them
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from an X* or from another guarded pointer of the same type. You
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can compare them with each other using operator==() and
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operator!=(), or test for 0 with isNull(). And you can dereference
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them using either the \c *x or the \c x->member notation.
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A guarded pointer will automatically cast to an X*, so you can
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freely mix guarded and unguarded pointers. This means that if you
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have a TQGuardedPtr<TQWidget>, you can pass it to a function that
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requires a TQWidget*. For this reason, it is of little value to
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declare functions to take a TQGuardedPtr as a parameter; just use
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normal pointers. Use a TQGuardedPtr when you are storing a pointer
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over time.
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Note again that class \e X must inherit TQObject, or a compilation
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or link error will result.
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*/
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/*!
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\fn TQGuardedPtr::TQGuardedPtr()
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Constructs a 0 guarded pointer.
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\sa isNull()
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*/
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/*!
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\fn TQGuardedPtr::TQGuardedPtr( T* p )
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Constructs a guarded pointer that points to same object as \a p
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points to.
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*/
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/*!
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\fn TQGuardedPtr::TQGuardedPtr(const TQGuardedPtr<T> &p)
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Copy one guarded pointer from another. The constructed guarded
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pointer points to the same object that \a p points to (which may
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be 0).
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*/
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/*!
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\fn TQGuardedPtr::~TQGuardedPtr()
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Destroys the guarded pointer. Just like a normal pointer,
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destroying a guarded pointer does \e not destroy the object being
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pointed to.
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*/
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/*!
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\fn TQGuardedPtr<T>& TQGuardedPtr::operator=(const TQGuardedPtr<T> &p)
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Assignment operator. This guarded pointer then points to the same
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object as \a p points to.
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*/
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/*!
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\overload TQGuardedPtr<T> & TQGuardedPtr::operator=(T* p)
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Assignment operator. This guarded pointer then points to the same
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object as \a p points to.
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*/
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/*!
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\fn bool TQGuardedPtr::operator==( const TQGuardedPtr<T> &p ) const
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Equality operator; implements traditional pointer semantics.
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Returns TRUE if both \a p and this guarded pointer are 0, or if
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both \a p and this pointer point to the same object; otherwise
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returns FALSE.
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\sa operator!=()
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*/
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/*!
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\fn bool TQGuardedPtr::operator!= ( const TQGuardedPtr<T>& p ) const
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Inequality operator; implements pointer semantics, the negation of
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operator==(). Returns TRUE if \a p and this guarded pointer are
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not pointing to the same object; otherwise returns FALSE.
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*/
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/*!
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\fn bool TQGuardedPtr::isNull() const
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Returns \c TRUE if the referenced object has been destroyed or if
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there is no referenced object; otherwise returns FALSE.
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*/
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/*!
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\fn T* TQGuardedPtr::operator->() const
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Overloaded arrow operator; implements pointer semantics. Just use
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this operator as you would with a normal C++ pointer.
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*/
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/*!
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\fn T& TQGuardedPtr::operator*() const
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Dereference operator; implements pointer semantics. Just use this
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operator as you would with a normal C++ pointer.
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*/
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/*!
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\fn TQGuardedPtr::operator T*() const
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Cast operator; implements pointer semantics. Because of this
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function you can pass a TQGuardedPtr\<X\> to a function where an X*
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is required.
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*/
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/* Internal classes */
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TQGuardedPtrPrivate::TQGuardedPtrPrivate( TQObject* o)
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: TQObject(0, "_ptrpriv" ), obj( o )
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{
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if ( obj )
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connect( obj, TQ_SIGNAL( destroyed() ), this, TQ_SLOT( objectDestroyed() ) );
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}
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TQGuardedPtrPrivate::~TQGuardedPtrPrivate()
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{
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}
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void TQGuardedPtrPrivate::reconnect( TQObject *o )
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{
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if ( obj == o )
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return;
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if ( obj )
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disconnect( obj, TQ_SIGNAL( destroyed() ),
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this, TQ_SLOT( objectDestroyed() ) );
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obj = o;
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if ( obj )
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connect( obj, TQ_SIGNAL( destroyed() ),
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this, TQ_SLOT( objectDestroyed() ) );
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}
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void TQGuardedPtrPrivate::objectDestroyed()
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{
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obj = 0;
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}
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