Re: [Boost-users] Problem with shared_ptr

Subject: Re: [Boost-users] Problem with shared_ptr
From: Nikolai N Fetissov (nikolai-boost_at_[hidden])
Date: 2009-01-18 17:37:29

> What's wrong with this code? When I push_back ptr to the vector, it pushes
> 0
> instead of
> the value contained in ptr (which I checked and is non-zero).
>
>
> std::vector<boost::shared_ptr<BaseClass> > baseobjects =
> get_base_objects(path);
>
>
>     std::vector<boost::shared_ptr<DerivedClass> >
> result(get_base_objects.size());

Your problem is the line above.
You're creating a vector of 'get_base_objects.size()' default-constructed
shared pointers. Either use reserve() to grab that much space, or use
assignment bellow.

>     BOOST_FOREACH (boost::shared_ptr<BaseClass> en, baseobjects)
>     {
>         boost::shared_ptr<DerivedClass> ptr =
> boost::dynamic_pointer_cast<DerivedClass>(en);
>
>         //Error when push_back. Instead of ptr, I get 0
>         result.push_back(ptr);
>     }

--
 Nikolai