RE: [Boost-Users] Re: Use a shared_ptr as a 'backpointer'?

From: Mark Storer (mstorer_at_[hidden])
Date: 2002-09-30 11:36:12

I've got a comment and a question...

1) Couldn't the "backpointer" just be a constant reference?  Backpointers,
in my mind, don't have anything to do with ownership, so a shared_ptr
woulnd't be appropriate.

2) shared_from_this?
        I can't find that one in any of the headers or docs I downloaded
with 1.28.  I did find shared_count in (oddly enough) shared_count.hpp,
which looks like it would prevent two seperate shared_ptr's from causing a
double-delete... pretty slick, but I couldn't find any docs on it.

--Mark Storer
  Software Engineer
  Cardiff Software

#include <disclaimer>
typedef std::disclaimer<Cardiff> Discard;

-----Original Message-----
From: David Abrahams [mailto:yg-boost-users_at_[hidden]]
Sent: Sunday, September 29, 2002 4:12 PM
To: boost-users_at_[hidden]
Subject: [Boost-Users] Re: Use a shared_ptr as a 'backpointer'?

<dick.bridges_at_[hidden]> wrote in message
news:OF699D7956.EED22A4F-ON88256C43.00722AD0_at_tais.net...
> I run into situations where it's useful for an object to have a
> 'backpointer' to the object instance that created it (example below).  Is
> there a pattern/idiom for doing this using shared_ptr?  Or maybe I need to
> re-think the idea of the backpointer in the first place?
>

class Bar;

class Foo
{
 public:
    Foo(shared_ptr<Bar>);

 private:
    shared_ptr<Bar> p;
};

class Bar : boost::shared_count
{
    void doit()
    {
         new Foo(boost::shared_from_this(this));     // <<< new Foo(this)
obviously won't work.
    }
};

HTH,
Dave

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