shared_ptr as class member

Question

It's common to declared contained objects as a pointers to that class, while "forward declarating" them in header file. This in order to reduce physical dependencies in code.

For example

class B;  // forward declaration   

class A {
   private:
      B* pB;
};

Would it be good idea to declare such a member as shared_ptr, instead of naked pointer?

I would prefer scoped_ptr, but AFAIK it it won't be in standard.

Answer 1

Yes you can (should ?).

This is a common practice. As you stated it avoids the need to explicitely call delete().

You can go even further. Here is an example:

class RSAKey
{
  public:

    RSAKey();

  private:

    shared_ptr<RSA> d_rsa; // A pointer to a RSA structure from OpenSSL
}

Which I initialize like this:

RSAKey::RSAKey()
{
  RSA* rsa = RSA_generate_key(1024, 1, NULL, NULL);

  if (NULL == rsa) throw DummyException();

  d_rsa.reset(rsa, RSA_free); // Note the specific release method.
}

When d_rsa will no longer be used, an automatic call to RSA_free() will occur. Isn't that cool ?!

---

Update

If C++11 is an option, you should probably better use std::unique_ptr instead which has less overhead and is movable.

It depends on how you want your enclosing class to behave in regards to copy.