Re: [Boost-users] typecasting a boost::shared_ptr ?

From: Vaclav Vesely (vaclav.vesely_at_[hidden])
Date: 2006-03-24 09:10:19

Dhanvi Kapila wrote:
>  I have a boost::shared_ptr that stores a pointer to a base class ( 
> class B1 ) and derived classes ( class D1 , class D2 )  both inheriting 
> from the same Base class.
>  The Constructors
> I have another set of factory classes ( base class : class base1, 
> derived class : class derv1 & class derv2 ) whoose constructors accepts 
> boost::shared_ptr of B1.
> 
> When constructing derv1: I would like to cast pointer as D1 and ,when 
> constructing derv2 : cast pointer as  D2,  but the only way I can access 
> the class functions is through a shared_ptr to B1.
> 
> My question is how do I cast B1 to get D1 and D2 in the constructors for 
> derv1 and derv2 respectively ?
> 
> base1* createBase( boost::shared_ptr<B1> b_ptr , int type )
> {
> 
>        if( type == 1 )
>           return new derv1( boost::polymorphic_downcast<AAAA> b_ptr );
>        else
>           return new derv2( boost::polymorphic_downcast<XXXX> b_ptr );
> }
> 
> what do i write in the place of AAAA & XXXX  for the code to wrk ??

What about

        return new derv1( boost::dynamic_pointer_cast<B1>(b_ptr));

see http://www.boost.org/libs/smart_ptr/shared_ptr.htm#dynamic_pointer_cast

Regards,
Vaclav