[util.smartptr.enab] (original) (raw)

20 General utilities library [utilities]

20.11 Smart pointers [smartptr]

20.11.6 Class template enable_­shared_­from_­this [util.smartptr.enab]

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 { };

int main() { shared_ptr p(new X); shared_ptr 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 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 shared_from_this(); shared_ptr shared_from_this() const; weak_ptr weak_from_this() noexcept; weak_ptr weak_from_this() const noexcept;

private: mutable weak_ptr weak_this; // exposition only }; }

The template parameter T of enable_­shared_­from_­thismay be an incomplete type.

constexpr enable_shared_from_this() noexcept; enable_shared_from_this(const enable_shared_from_this<T>&) noexcept;

Effects:Value-initializes weak_­this.

enable_shared_from_this<T>& operator=(const enable_shared_from_this<T>&) noexcept;

[ Note

:

weak_­this is not changed.

— end note

]

shared_ptr<T> shared_from_this(); shared_ptr<T const> shared_from_this() const;

Returns: shared_­ptr<T>(weak_­this).

weak_ptr<T> weak_from_this() noexcept; weak_ptr<T const> weak_from_this() const noexcept;