Question

So we have (pseudo code):

class A
{
 A(shared_ptr parent){}
}

class B
{
 A *a;
 B()
 {
  a = new A(boost::shared_ptr(this));
 }
}

Is it possible to do such thing with shared_ptr in C++ and how to do it in real C++ code?

Answer 1

You need enable_shared_from_this:

#include <memory>

class B : public std::enable_shared_from_this<B>
{
  A * a;
public:
  B() : a(new A(std::shared_from_this())) { }
};

(This is for C++0x; Boost should work similarly.)

Just making a shared pointer from this is tricky because you might shoot your own foot off. Inheriting from enable_shared_from_this makes this easier.

Word of warning: Your construction with the naked A pointer seems to defeat the purpose of using resource-managing classes. Why not make a into a smart pointer, too? Maybe a unique_ptr?