Re: [boost] Request for data-member smart pointer

From: Alexander Nasonov (alnsn_at_[hidden])
Date: 2004-10-07 00:08:55

Peter Dimov wrote:
> This is a bit harder.
> 
> class A
> {
> private:
> 
>    WORD m_wData;
> 
> private:
> 
>    A();
> 
> public:
> 
>    static shared_ptr<A> CreateA() { return shared_ptr<A>(new A); }
> 
>    friend shared_ptr<WORD> GetData( shared_ptr<A> this_ )
>    {
>        return shared_ptr<WORD>(
>            &this_->m_wData,
>            boost::bind( &shared_ptr<A>::reset, this_ )
>        );
>    }
> };
> 
> int main()
> {
>    shared_ptr<A> pa = A::CreateA();
>    shared_ptr<WORD> pw = GetData(pa);
>    pa.reset();
>    std::cout << "*pw: " << *pw << '\n';
> }

I'm implementing a mixture of smart_ptr and boost.langbinding libraries.
It's in early stage and I don't know yet what it's best for. Candidate
number one is a transaction framework.
Pointers to objects are smart, of course. They always point to full
object and they store dynamic type of the object. Plus, smart pointers
hold a pointer to static type.
You can clone and swap pointee object. And you can extact a member from
it.

object_ptr<Y> py(new Y);
object_ptr<X> px = py.get_member(&Y::x);

// Works even though static types are unknown:
object_ptr<void> pvy(py);
object_ptr<void> pvx py.get_member(&Y::x);

// Other operations:
object_ptr<void> copy = pvx.clone();
copy.swap_object(pvx);

-- 
Alexander Nasonov