# std::enable_shared_from_this<T>::shared_from_this

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< cpp‎ | memory‎ | enable shared from this

shared_ptr<T> shared_from_this(); | (1) |
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 (C++11) | smart pointer with shared object ownership semantics (class template)

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