Is there a smart pointer that is automatically nulled when its target is destroyed in C++

Question

I've found QPointer. Are there any others?

score 8 · Accepted Answer · answered May 26 '09 at 08:11

Boost - the weak_ptr has some nice features that make it safe to use, if you are also using shared_ptr. You keep a weak_ptr reference to an instance that is managed by shared_ptr lifetime. When you need to use the underlying instance, convert it to a shared_ptr instance using the constructor of the shared_ptr class, or the lock method. The operation will fail if the underlying instance was deleted. The use is thread safe in the same fashion as the shared_ptr class:

shared_ptr<int> p(new int(5));
weak_ptr<int> q(p);

// some time later

if(shared_ptr<int> r = q.lock())
{
    // use *r
}

Thanks. I wasn't aware that weak_ptr had this behaviour. I wonder how much I'm paying for the unneeded reference counting behaviour though. Anyway, your answer was first, I think. Marking as best. — Neil G, May 26 '09 at 17:55

score 6 · Answer 2 · answered May 26 '09 at 08:10

6

"boost::weak_ptr" works really well with "boost::shared_ptr" (also available in tr1)

answered May 26 '09 at 08:10

stefaanv

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Is there a smart pointer that is automatically nulled when its target is destroyed in C++

2 Answers2

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