Re: [boost] [shared_ptr] enable_shared_from_any ?

Subject: Re: [boost] [shared_ptr] enable_shared_from_any ?
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2010-05-17 09:20:34

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On Saturday 15 May 2010, Philip Warner wrote:
> And yes, this is sloppy, but in our case we have a set of interfaces
> that want to implement variant function return types based on derived
> class pointers, and we can not do that by returning shared_ptr objects.
> We need to return raw pointers, then rewrap them.

Are you saying you want to have a covariant return types with shared_ptr?  
Have you considered doing something like the following (completely untested):

class Base
{
        typedef X FReturnType;
private:
        template<typename T>
        friend shared_ptr<T::FReturnType> g(T &t);
        virtual FReturnType* f();
};
class Derived: public Base
{
public:
        typedef DerivedFromX FReturnType;
private:
        template<typename T>
        friend shared_ptr<T::FReturnType> g(T &t);
        virtual FReturnType* f();
}
template<typename T>
shared_ptr<typename T::FReturnType> g(T &t)
{
        return shared_ptr<typename T::FReturnType>(t.f());
}

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