Containers, Smart Pointers and Templated Inherited Classes

Question

I can compile some code which fills a vector of raw pointers to a base class with pointers to a templated inherited class. But I've tried using the standard library and boost smart pointers instead of raw pointers, and the code doesn't compile. Can you explain why not?

This works:

vector<base*> vec
inherited<double>* elem = new inherited<double> >();
vec.push_back(elem);

This doesn't:

vector<auto_ptr<base> > vec
auto_ptr<inherited<double> >(new inherited<double> >());
vec.push_back(elem);

I don't really care whether or not what I'm trying to do is reasonable I'm just feeling out what's possible.

My full 60 LOC is here: https://gist.github.com/melvyniandrag/f432140c1aa216696bb6

Don't beat me up guys I've read a bit of C++ Templates: The Complete Guide (2002) and some posts here, but haven't been able to expediently connect the dots.

Answer 1

You can do this using std::shared_ptr and std::static_pointer_cast .

vector<shared_ptr<base> > vec;
shared_ptr<inherited<double> > elem(new inherited<double> >());
vec.push_back(static_pointer_cast<inherited<double>,base>(elem));