A class T can inherit from enable_shared_from_this<T> to inherit the shared_from_this member functions that obtain a shared_ptr instance pointing to *this.
[ Example:
struct X: public enable_shared_from_this<X> { };
int main() {
shared_ptr<X> p(new X);
shared_ptr<X> q = p->shared_from_this();
assert(p == q);
assert(!p.owner_before(q) && !q.owner_before(p)); // p and q share ownership
}
— end example ]
namespace std {
template<class T> class enable_shared_from_this {
protected:
constexpr enable_shared_from_this() noexcept;
enable_shared_from_this(const enable_shared_from_this&) noexcept;
enable_shared_from_this& operator=(const enable_shared_from_this&) noexcept;
~enable_shared_from_this();
public:
shared_ptr<T> shared_from_this();
shared_ptr<T const> shared_from_this() const;
weak_ptr<T> weak_from_this() noexcept;
weak_ptr<T const> weak_from_this() const noexcept;
private:
mutable weak_ptr<T> weak_this; // exposition only
};
}
constexpr enable_shared_from_this() noexcept;
enable_shared_from_this(const enable_shared_from_this<T>&) noexcept;
enable_shared_from_this<T>& operator=(const enable_shared_from_this<T>&) noexcept;
shared_ptr<T> shared_from_this();
shared_ptr<T const> shared_from_this() const;
weak_ptr<T> weak_from_this() noexcept;
weak_ptr<T const> weak_from_this() const noexcept;