boost::shared_ptr and this

As a good introduction to some of the most interesting boost libraries you can read "Beyond the C++ Standard Library: An Introduction to Boost", by Björn Karlsson, an Addison Wesley Professional book. That's what I'm actually doing, and these are a few notes that I'm jotting down in the meanwhile.

Let's say we have a class A, and we want to call from one of its methods a free function that accept as input parameter a shared_ptr to A.

There is a relatively simple way to get it. We could let our class A derive from enable_shared_from_this<A> and use shared_from_this() to get the shared_ptr.

Here is a short example that shows this feature:

#include <iostream>
#include "boost/shared_ptr.hpp"
#include "boost/enable_shared_from_this.hpp"

using std::cout;
using std::endl;
using boost::shared_ptr;
using boost::enable_shared_from_this;

namespace
{
    class A;
    void doStuff(shared_ptr<A> p);

    class A : public enable_shared_from_this<A>
    {
    public:
        void callDoStuff()
        {
            cout << "in A::callDoStuff()" << endl;
            doStuff(shared_from_this());
        }

        void cheers() { cout << "Cheers from A" << endl; }
    };

    void doStuff(shared_ptr<A> p)
    {
        cout << "Doing stuff in doStuff()" << endl;
        p->cheers();
    }
}

void sharedThis()
{
    shared_ptr<A> p(new A());
    p->callDoStuff();
}