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std::shared_ptr<T>:: swap

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

저장된 포인터 값과 * this 와 r 의 소유권을 교환합니다. 참조 카운트가 있는 경우 조정되지 않습니다.

매개변수

r - 내용을 교환할 스마트 포인터

반환값

(없음)

예제

이 코드 실행 
#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();   
}

출력: 

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