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std:: swap (std::shared_ptr)

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swap (std::shared_ptr)
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定义于头文件 <memory>
template < class T >
void swap ( std:: shared_ptr < T > & lhs, std:: shared_ptr < T > & rhs ) noexcept ;
(C++11 起)

为 std::swap 算法特化 std:: shared_ptr 。交换 lhs 和 rhs 的内容。调用 lhs. swap ( rhs ) 。


目录

参数

lhs, rhs - 要交换内容的智能指针

返回值

(无)

复杂度

常量。

示例

运行此代码 
#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();
    std::swap(p1, p2);
    print();
    p1.reset();
    print();
    std::swap(p1, p2);
    print();   
}

输出： 

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

另请参阅

交换两个对象的值
(函数模板)
交换内容
(公开成员函数)