C++11中std::function基础用法详解

std::function<return_type(parameter_types)> var_name;

int func(int x, int y) { return x + y; }
std::function<int(int, int)> f = func;
class A {
public:
    int mem_func(int x) { return x * x; }
};
std::function<int(A*, int)> f2 = &A::mem_func;

std::function<int(int, int)> f;
if (f)
    std::cout << f(1, 2) << std::endl;
else
    std::cout << "f is empty" << std::endl;

#include <iostream>
#include <functional>
void test1(){std::cout<<"function"<<std::endl;}
int test2(int i){ return i; }
int test3(int i, int j){ return i+j; }
struct A{
    void foo(int i){ std::cout<<i<<std::endl; }
};
int main() {
    std::function<void()> fn1 = std::bind(test1);
    std::function<int(int)> fn2 = std::bind(test2, std::placeholders::_1);
    std::function<int(int, int)> fn3 = std::bind(test3, std::placeholders::_1, std::placeholders::_2);
    std::function<int(int)> fn4 = std::bind(test3, 3, std::placeholders::_1);
    std::function<int()> fn5 = std::bind(test3, 3, 4);
    A a;
    std::function<void(int)> fn6 = std::bind(&A::foo, &a, std::placeholders::_1);
    fn1();
    std::cout<<fn2(1)<<std::endl;
    std::cout<<fn3(2, 3)<<std::endl;
    std::cout<<fn4(3)<<std::endl;
    std::cout<<fn5()<<std::endl;
    fn6(8);
}

std::function<int(int, int)> add = std::make_shared<int(*)(int, int)>([](int a, int b) { return a + b; });

class A {
public:
    int add(int a, int b) { return a + b; }
};
std::function<int(A&, int, int)> add = &A::add;
A a;
std::cout << add(a, 3, 4) << std::endl;

std::function<int(int)> add3 = std::bind([](int a, int b) { return a + b; }, 3, std::placeholders::_1);
std::cout << add3(4) << std::endl;