[Uml-devel] dynamic_cast usage

[Carsten Pfeiffer]

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Hiya,

I found many dynamic_casts in umbrello, while most of them should be 
static_casts, I think.

I.e. there is not much point in doing

return dynamic_cast<StateWidgetData *>( m_pData ) -> getActivityList();

dynamic_cast performs a runtime type-check and returns a valid pointer 
(StateWidgetData * here) IF the to be casted pointer is of that type or a 
subtype thereof. Otherwise it returns a 0L-pointer.

So, if you know that m_pData is a StateWidgetData, then you should use

return static_cast<StateWidgetData *>( m_pData ) -> getActivityList();

because static_cast doesn't involve dynamic typechecking (i.e. it is a bit 
faster).

You need to use dynamic_cast if you don't know if m_pData points to an object 
of type StateWidgetData or SomeOtherWidgetData. I.e. if you have a common 
baseclass but you need to call a method that is only in one of specific 
subclasses.

Then you do:

StateWidgetData *swd = dynamic_cast<StateWidgetData *>( m_pData );
if ( swd )
	return swd->getActivityList();
else
	[...]


Another thing I just noticed: deleting a 0L-pointer is perfectly valid, i.e. 
there is no need check for non-0L before deleting something, like
if ( foo )
	delete foo;

Cheers
Carsten Pfeiffer
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