std::shared_ptr<T>::swap

 

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std::shared_ptr

Member functions

shared_ptr::shared_ptr

shared_ptr::~shared_ptr

shared_ptr::operator=

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shared_ptr::reset

shared_ptr::swap

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shared_ptr::get

shared_ptr::operator*shared_ptr::operator->

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shared_ptr::operator bool

shared_ptr::owner_before

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std::swap

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static_pointer_castdynamic_pointer_castconst_pointer_castreinterpret_pointer_cast (C++17)

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operator<<

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std::atomic<std::shared_ptr> (C++20)

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void swap( shared_ptr& r ) noexcept;		(since C++11)

Exchanges the stored pointer values and the ownerships of *this and r. Reference counts, if any, are not adjusted.

Parameters

r

-

smart pointer to exchange the contents with

Return value

(none)

Example

Run this code

#include <iostream>
#include <memory>
#include <string>
 
struct Foo {
    Foo(int _val) : val(_val) { std::cout << "Foo...\n"; }
    ~Foo() { std::cout << "~Foo...\n"; }
    std::string print() { return std::to_string(val); }
    int val;
};
 
int main()
{
    std::shared_ptr<Foo> p1 = std::make_shared<Foo>(100);
    std::shared_ptr<Foo> p2 = std::make_shared<Foo>(200);
    auto print = [&]() {
        std::cout << " p1=" << (p1 ? p1->print() : "nullptr");
        std::cout << " p2=" << (p2 ? p2->print() : "nullptr") << '\n';  
    };
    print();
 
    p1.swap(p2);
    print();
 
    p1.reset();
    print();
 
    p1.swap(p2);
    print();   
}

Output:

Foo...
Foo...
 p1=100 p2=200
 p1=200 p2=100
~Foo...
 p1=nullptr p2=100
 p1=100 p2=nullptr
~Foo...