[Boost-users] Re: smart_ptr and self-referencing objects?

From: David Abrahams (dave_at_[hidden])
Date: 2005-03-24 16:53:42

edA-qa mort-ora-y <eda-qa_at_[hidden]> writes:

> I am in the process of converting a library of ours (which used a 
> Refcounting mechanism for shared objects) to be buildable on top of the 
> boost smart_ptr library*.
>
> What feature I am having the most difficulty with is the ability for an 
> object to refer to itself and be properly shared.  That is, by quick 
> example:
>
> /////////////////////////////
> class A {
>     void Do( B* b )
>         { b->Add( this ); }    //trouble line
> }
>
> class B {
>     vector::shared_ptr<A> items;
>     void Add( A* a )
>         { items.push_back( a ); }
> }
>
> ...
> shared_ptr<A> a( new A() );
> shared_ptr<B> b( new B() );
>
> a->Do( b );    //hidden problems
> ///////////////////////////////
>
> In the trouble line I am having a problem since I need to refer to this, 
> but it will not be referring to the shared_ptr wrapper on the object. 
> Thus it will end up being delete'd twice.

Have a look at enable_shared_from_this:

http://www.boost.org/libs/smart_ptr/enable_shared_from_this.html

HTH,

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com