How does one downcast a std::shared_ptr?

Question

Consider:

struct SomethingThatsABase {     virtual bool IsChildOne() const { return false; }     virtual bool IsChildTwo() const { return false; } };  struct ChildOne : public SomethingThatsABase {     virtual bool IsChildOne() const { return true; } };  struct ChildTwo : public SomethingThatsABase {     virtual bool IsChildTwo() const { return true; } };  void SomeClientExpectingAChildOne(std::shared_ptr<ChildOne> const& ptrOne) {     //Does stuff }  void SomeClient(std::shared_ptr<SomethingThatsABase> const& ptr) {     if (ptr->IsChildOne())     {         SomeClientExpectingAChildOne(ptr); //Oops.         //Hmm.. can't static_cast here, because we need a `shared_ptr` out of it.     } } 

(Note that I can't simply do a std::shared_ptr<ChildOne>(static_cast<ChildOne*>(ptr.get())), because then the reference counts don't get shared between the two shared_ptrs)

Answer 1

This ought to work:

if (ptr->IsChildOne()) {     SomeClientExpectingAChildOne(std::static_pointer_cast<ChildOne>(ptr)); } 

Answer 2

The shared_ptr equivalent of static_cast is static_pointer_cast, and the shared_ptr equivalent of dynamic_cast is dynamic_pointer_cast.