NAME¶

std::enable_shared_from_this::shared_from_this - std::enable_shared_from_this::shared_from_this

Synopsis¶

std::shared_ptr<T> shared_from_this(); (1)
std::shared_ptr<T const> shared_from_this() const; (2)

Returns a std::shared_ptr<T> that shares ownership of *this with all existing
std::shared_ptr that refer to *this.

Effectively executes std::shared_ptr<T>(weak_this), where weak_this is the private
mutable std::weak_ptr<T> member of enable_shared_from_this.

Notes¶

It is permitted to call shared_from_this only on a previously shared object, i.e. on
an object managed by std::shared_ptr (in particular, shared_from_this cannot be
called during construction of *this).

Otherwise
the behavior is undefined
(until C++17)
std::bad_weak_ptr is thrown (by the shared_ptr constructor from a
default-constructed weak_this)
(since C++17).

Return value¶

std::shared_ptr<T> that shares ownership of *this with pre-existing std::shared_ptrs

Example¶

// Run this code

#include <iostream>
#include <memory>

struct Foo : public std::enable_shared_from_this<Foo> {
Foo() { std::cout << "Foo::Foo\n"; }
~Foo() { std::cout << "Foo::~Foo\n"; }
std::shared_ptr<Foo> getFoo() { return shared_from_this(); }
};

int main() {
Foo *f = new Foo;
std::shared_ptr<Foo> pf1;

{
std::shared_ptr<Foo> pf2(f);
pf1 = pf2->getFoo(); // shares ownership of object with pf2
}

std::cout << "pf2 is gone\n";
}

Output:¶

Foo::Foo
pf2 is gone
Foo::~Foo

See also¶

shared_ptr smart pointer with shared object ownership semantics
(C++11) (class template)