static_cast with boost :: shared_ptr？

Question

什么是一个相当于static_cast用boost::shared_ptr？

换句话说,我该如何重写以下内容

Base* b = new Derived();
Derived* d = static_cast<Derived*>(b);

什么时候用shared_ptr？

boost::shared_ptr<Base> b(new Derived());
boost::shared_ptr<Derived> d = ???

Answer 1

用途boost::static_pointer_cast:

boost::shared_ptr<Base> b(new Derived());
boost::shared_ptr<Derived> d = boost::static_pointer_cast<Derived>(b);

Answer 2

有三种类型转换操作符的智能指针:static_pointer_cast,dynamic_pointer_cast,和const_pointer_cast.它们位于命名空间boost(由提供者<boost/shared_ptr.hpp>)或命名空间std::tr1(由Boost或编译器的TR1实现提供).