shared_from_this called from constructor

Question

I have to register an object in a container upon its creation. Without smart pointers I\'d use something like this:

a_class::a_class()
{
    register_somewhere(t         


        

Answer 1

Why don't you use http://www.boost.org/doc/libs/1_43_0/libs/smart_ptr/enable_shared_from_this.html

struct a_class : enable_shared_from_this {
    a_class() {
        shared_ptr ptr(this);
        register_somewhere(ptr);
    }
};

Update: here is a complete working example:

#include 
#include 

struct a_class;
boost::shared_ptr pa;

void register_somewhere(boost::shared_ptr p)
{
    pa = p;
};

struct a_class : boost::enable_shared_from_this {
private:
    a_class() {
        printf("%s\n", __PRETTY_FUNCTION__);
        boost::shared_ptr ptr(this);
        register_somewhere(ptr);
    }

public:
    ~a_class() {
        printf("%s\n", __PRETTY_FUNCTION__);
    }

    static boost::shared_ptr create()
    {
        return (new a_class)->shared_from_this();
    }
};

int main()
{
    boost::shared_ptr p(a_class::create());
}

Note the factory function a_class::create(). Its job is to make sure that only one reference counter gets created. Because

boost::shared_ptr p(new a_class);

Results in creation of two reference counters and double deletion of the object.