On Fri, 23 Oct 2009, Pritpal Bedi wrote:
Hi,
> If a class contains all the methods it is implementing then this
> code will definitely work excellent. But what if the call is inheriting
> from other which in turn again inheriting from one more, and
> a method is called from parent two levels up. The same
> pointer is passed along the class hirarchy which is typecasted
> to parent class's pointer.
Maybe you should think about introducing some support for references
chains updated automatically by child classes.
First time when object of given class is created it registers in parent
class alternative function to extract from parameter the object pointer
casted to parent class. Below is a code scheme which implements it.
best regards,
Przemek
/* global declaration */
typedef void * ( * QT_PARAM_FUNC ) ( int );
typedef struct _QT_PARAM_INFO
{
QT_PARAM_FUNC pFunc;
struct _QT_PARAM_INFO * pNext;
BOOL fInited;
} QT_PARAM_INFO;
/* this function is part of QDialog wrapper */
extern void qt_childregister_QDialog( QT_PARAM_INFO * paramInfo );
/*** QPageSetupDialog.cpp ***/
[...]
static HB_GARBAGE_FUNC( release_QPageSetupDialog )
{
QPointer< QPageSetupDialog > * pObj =
( QPointer< QPageSetupDialog > * ) Cargo;
QPageSetupDialog * obj = * pObj;
if( obj )
{
*pObj = NULL;
delete obj;
}
}
static const HB_GC_FUNCS s_gcQPageSetupDialog =
{
release_QPageSetupDialog,
hb_gcDummyMark
};
static QT_PARAM_INFO s_paramInfo;
static QT_PARAM_INFO * s_paramList = NULL;
/* public function use by descendant classes to register their
* param functions
*/
void qt_childregister_QPageSetupDialog( QT_PARAM_INFO * paramInfo )
{
if( !paramInfo->fInited )
{
/* TODO: add MT protection in fianl version */
paramInfo->fInited = TRUE;
paramInfo->pNext = s_paramList;
s_paramList = paramInfo;
}
}
/* public function which extracts pointer to QPageSetupDialog object
* from given HVM parameter. This parameter may contain also any
* descendant class which register its param function using
* qt_childregister_QPageSetupDialog().
*/
QPageSetupDialog * hbqt_par_QPageSetupDialog( int iParam )
{
QPointer< QPageSetupDialog > * pObj;
QPageSetupDialog * obj = NULL;
pObj = ( QPointer< QPageSetupDialog > * )
hb_parptrGC( &s_gcQPageSetupDialog, iParam );
if( pObj == NULL )
{
/* Not a QPageSetupDialog pointer item, check all registered
* descendant classes
*/
QT_PARAM_INFO * paramInfo = s_paramList;
while( paramInfo )
{
pObj = ( QPointer< QPageSetupDialog > * )
paramInfo->pFunc( iParam );
if( pObj )
break;
paramInfo = paramInfo->pNext;
}
}
if( pObj == NULL )
{
/* RT ERROR - wrong parameter */
}
else
{
obj = * pObj;
if( obj == NULL )
{
/* RT ERROR - object deleted by other code */
}
}
return obj;
}
QPointer< QPageSetupDialog > * qt_alloc_QPageSetupDialog( void )
{
QPointer< QPageSetupDialog > * pObj;
if( !s_paramInfo.fInited )
{
/* First call - register in parent class our param function */
s_paramInfo.pFunc = ( QT_PARAM_FUNC ) hbqt_par_QPageSetupDialog;
qt_childregister_QDialog( &s_paramInfo );
/* if class inherits directly from more then one classes
* (multiinheritance) then for each parent class register
* coresponding s_paramInfo<X> parameter
*/
}
pObj = ( QPointer< QPageSetupDialog > * )
hb_gcAllocate( sizeof( QPointer< QPageSetupDialog > ),
&s_gcQPageSetupDialog );
return pObj;
}
HB_FUNC( QT_QPAGESETUPDIALOG )
{
QPointer< QPageSetupDialog > * pObj = qt_alloc_QPageSetupDialog();
if( hb_pcount() >= 2 )
*pObj = new QPageSetupDialog( hbqt_par_QPrinter( 1 ),
hbqt_par_QWidget( 1 ) );
else
*pObj = new QPageSetupDialog( hbqt_par_QWidget( 1 ) );
hb_retptrGC( pObj );
}
HB_FUNC( QT_QPAGESETUPDIALOG_EXEC )
{
QPageSetupDialog * obj = hbqt_par_QPageSetupDialog( 1 );
if( obj )
hb_retni( obj->exec() );
}
[...]
_______________________________________________
Harbour mailing list
Harbour@harbour-project.org
http://lists.harbour-project.org/mailman/listinfo/harbour
