Re: [Somelib] Errors with downcasting using SOME::Object

[Frank V. C. <fr...@co...>]

You were right the first time, SOME::Object is not a class in the
hierarchy and once you instantiate it:

--> SOME::Object<mriIVisualAsset>oAsset(assets[0]);

it IS only a SOME::Object/shared_ptr<mriVisualAsset>, but looking at the
shared_ptr, you should be able to:

--> mriAsset *asset = oAsset;

which should call the coercion operator on boost::shared_ptr. At least
that's how it behaves (compiles, runs without error) for me in the
attached emulation test.
 
"John Palmieri (Quinticent)" wrote:
> 
> Linux/gcc -
> 
> Hierarchy:
> 
>               mriIAsset
>                    /    \
>                  /        \
> mriIVisualAsset   mriIAudioAsset    (There will be more in the future)
> 
> I think the whole problem is that SOMELib uses some sort of smart pointers
> that I haven't looked into.  Tom is using them in SOME::Object.
> 
> SOME::Object<T> expands to class SOME::Object : public boost_smart_ptr<T>
> 
> I haven't looked at the boost stuff and I am not sure if boost_smart_ptr isA
> T or hasA T.  If it is hasA this will have to change.  If it cannot be
> downcast then it needs to be taken out of SOMELib as I am not sure what
> benefits it gives.
> 
> -Quinticent
> 
> "Frank V. Castellucci" wrote:
> 
> > What is the hierarchy? You may need dynamic_cast<> based on the rules of
> > usage in 1998(E) C++ standard.
> > What is the error, and what is the compiler/platform?
> >
> > John Palmieri wrote:
> > >
> > > I am trying to integrate SOMELib into snaglepuss and am having errors
> > > with downcasting my objects.
> > >
> > > You see I have a hiarchy of interfaces for use with dynamicly loadable
> > > assets (png, mp3, mpg files).  They all get loaded and stuffed into
> > > chests which are just glorified vectors of type mriIAsset *.  Now each
> > > of the assets can be rendered to the screen, audio device, etc. with a
> > > call to the render() method.  But, each type of asset also has enhanced
> > > functionality based on their type so my png loader asset would also
> > > inherit the interface mriIVisualAsset which would in turn inherit the
> > > mriIAsset interface.  The problem I am having is that when I load my
> > > object I check to see if it is visual, audio.  Let's say it is a visual
> > > asset.  I then use this code to construct the object:
> > >
> > > SOME::Object<mriIVisualAsset>oAsset(assets[0]);
> > > //construct our asset
> > > if(!oAsset.construct()){ ...
> > >
> > > this works fine but now I want to add this asset to my chest:
> > >
> > > asset = static_cast<mriIAsset *>(oAsset);  //error here.  I'm guessting
> > > the template is not truly inheriting
> > >
> > > chest->addAsset( chestpos, asset );//I should be able to mix and match
> > > different assests in my chest
> > >
> > > This is an important feature and as much as I know you love the boost
> > > stuff if it restricts projects from using standard C++ mechanisms when
> > > working with SOMELib it will have to go.
> > >
> > > -Quinticent
> > >
> > > _______________________________________________
> > > somelib-devel mailing list
> > > som...@li...
> > > http://lists.sourceforge.net/mailman/listinfo/somelib-devel
> >
> > --
> > Frank V. Castellucci
> > http://corelinux.sourceforge.net
> > OOA/OOD/C++ Standards and Guidelines for Linux
> > http://PythPat.sourceforge.net
> > Pythons Pattern Package
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> 
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-- 
Frank V. Castellucci
http://corelinux.sourceforge.net
OOA/OOD/C++ Standards and Guidelines for Linux
http://PythPat.sourceforge.net
Pythons Pattern Package