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std::function::target

STD：：功能：目标

template< class T > T* target((1)(since C++11)
template< class T > const T* target() const;(2)(since C++11)

返回指向存储的可调用函数目标的指针。

参数

%280%29

返回值

指向存储函数的指针target_type() == typeid(T)，否则为空指针。

例外

noexcept规格：

noexcept

例

二次

#include <functional>
#include <iostream>
 
int f(int, int) { return 1; }
int g(int, int) { return 2; }
void test(std::function<int(int, int)> const& arg)
{
    std::cout << "test function: ";
    if (arg.target<std::plus<int>>())
        std::cout << "it is plus\n";
    if (arg.target<std::minus<int>>())
        std::cout << "it is minus\n";
 
    int (*const* ptr)(int, int) = arg.target<int(*)(int, int)>(
    if (ptr && *ptr == f)
        std::cout << "it is the function f\n";
    if (ptr && *ptr == g)
        std::cout << "it is the function g\n";
}
 
int main()
{
    test(std::function<int(int, int)>(std::plus<int>())
    test(std::function<int(int, int)>(std::minus<int>())
    test(std::function<int(int, int)>(f)
    test(std::function<int(int, int)>(g)
}

二次

产出：

二次

test function: it is plus
test function: it is minus
test function: it is the function f
test function: it is the function g

二次

另见

target_typeobtains the typeid of the stored target (public member function)

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