Boost库中对this指针的包装

class Y: public enable_shared_from_this<Y>

{

public:

shared_ptr<Y> f()

{

return shared_from_this();

}

}

int main()

{

shared_ptr<Y> p(new Y);

// 调用f获得shared_ptr

shared_ptr<Y> q = p->f();

assert(p == q);

assert(!(p < q || q < p)); // p and q must share ownership

}

template<class T> class enable_shared_from_this

{

protected:

enable_shared_from_this()

{

}

enable_shared_from_this(enable_shared_from_this const &)

{

}

enable_shared_from_this & operator=(enable_shared_from_this const &)

{

return *this;

}

~enable_shared_from_this()

{

}

public:

shared_ptr<T> shared_from_this()

{

shared_ptr<T> p(_internal_weak_this);

BOOST_ASSERT(p.get() == this);

return p;

}

shared_ptr<T const> shared_from_this() const

{

shared_ptr<T const> p(_internal_weak_this);

BOOST_ASSERT(p.get() == this);

return p;

}

// Note: No, you don't need to initialize _internal_weak_this

//

// Please read the documentation, not the code

//

// http://www.boost.org/libs/smart_ptr/enable_shared_from_this.html 
typedef T _internal_element_type; // for bcc 5.5.1

mutable weak_ptr<_internal_element_type> _internal_weak_this;

};