Re: [ROOT] Purely virtual base classes and streamers(?)

From: Volker Hejny (V.Hejny@fz-juelich.de)
Date: Sat Dec 01 2001 - 16:24:00 MET


Hallo Rene,

On Fri, Nov 30, 2001 at 02:25:47PM +0000, Rene Brun wrote:
> Hi Volker,
> 
> I have recently made changes in teh development version in CVS for situations
> like you describe. If you could provide a small test case corresponding to your
> exact situation, I could tell you if this new version fixes this problem.

In principle, you could test whether TArrayI is processed correctly, because
our case is basically the same, with the difference that the array will
not be recreated if the size is reduced. The behaviour in browsing is the
same.
 
> There are sometimes class constructions non trivial to support when
> an abstract class is found during the split mode. ROOT needs to build
> the dictionary for these classes. To build teh dictionary, an instance
> of the class has to be created. If the dictionary has not already been built
> when the abstract class is found, there is no way to make an instance.
> The difficulty is in detecting in the parent (real classes) this situation.

Well, abstract base classes are a nice instrument to define interfaces,
but for classes forseen to be written into a tree in split mode, it might 
be easy enough to avoid them. So if itīs tricky to support these cases,
a warning in the TTree documentation should do the job.

Best regards,
Volker

-- 
Dr. Volker Hejny                Tel: 02461/616853                      ** 
Institut f. Kernphysik          Fax: 02461/613930                     **
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