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std:: swap (std::function)

From cppreference.net
C++
Utilities library
Function objects
Function invocation
(C++17) (C++23)
Identity function object
(C++20)
Old binders and adaptors
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std::function
定义于头文件 <functional>
template < class R, class ... Args >
void swap ( std:: function < R ( Args... ) > & lhs, std:: function < R ( Args... ) > & rhs ) noexcept ;
(C++11 起)

为 std::swap 算法针对 std::function 提供重载版本。交换 lhs 与 rhs 的状态。实际等效调用 lhs. swap ( rhs ) 。

目录

参数

lhs, rhs - 需要交换状态的多态函数包装器

返回值

(无)

示例

运行此代码 
#include <functional>
#include <iostream>
void foo(const char* str, int x)
{
    std::cout << "foo(\"" << str << "\", " << x << ")\n";
}
void bar(const char* str, int x)
{
    std::cout << "bar(\"" << str << "\", " << x << ")\n";
}
int main()
{
    std::function<void(const char*, int)> f1{foo};
    std::function<void(const char*, int)> f2{bar};
    f1("f1", 1);
    f2("f2", 2);
    std::cout << "std::swap(f1, f2);\n";
    std::swap(f1, f2);
    f1("f1", 1);
    f2("f2", 2);
}

输出： 

foo("f1", 1)
bar("f2", 2)
std::swap(f1, f2);
bar("f1", 1)
foo("f2", 2)

缺陷报告

下列行为变更缺陷报告被追溯应用于先前发布的C++标准。

缺陷报告 应用于 发布时的行为 正确行为
LWG 2062 C++11 function 的 swap 重载未被要求为 noexcept 要求为 noexcept

参见

交换内容
(公开成员函数)
(C++23)
特化 std::swap 算法
(函数)