Re: [Boost-users] Boost.Signals2 - tracking an object managed with tr1::shared_ptr

Subject: Re: [Boost-users] Boost.Signals2 - tracking an object managed with tr1::shared_ptr
From: Frank Mori Hess (frank.hess_at_[hidden])
Date: 2009-09-14 15:15:29

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On Monday 14 September 2009, Monteleone, Nathan wrote:
>
> This is also interesting, although it doesn't help with the tr1 namespace
> woes:
> http://boost.org/libs/smart_ptr/sp_techniques.html#weak_without_shared The
> gist of it is that you can make any object support weak_ptr with an
> internal shared_ptr to itself, with a null_deleter.  Might be of interest
> for people wanting to track a wider variety of objects.

That's what signals2::trackable does.  It's not a thread-safe scheme though, 
since the contained shared_ptr doesn't really own the object.

One thing you could do is bind a weak_ptr as the "this" argument of the member 
function you are using as a slot, and define a get_pointer() function for 
your weak_ptr that throws an expired_slot exception when the weak_ptr 
expires, or returns a shared_ptr otherwise.  That would work almost the same 
as the track(), except the slot could only be removed from the slot list by 
signal invocations and not during connect() calls.

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