我正在尝试理解std::bind和std::function的工作原理。但是我无法使以下代码编译:
#include <iostream>
#include <string>
#include <functional>
void function(int a, float b, std::string const &s)
{
std::cout << "printing function" << std::endl;
std::cout << a << std::endl;
std::cout << b << std::endl;
std::cout << s << std::endl;
}
int main(int argc, char *argv[])
{
std::bind(&function, 10, 11.1, "hello")();
std::function<void(int, float, std::string const&)> fun = std::bind(&function, 10, std::placeholders::_1, std::placeholders::_2);
fun(0.2, "world");
return 0;
}
编译器抱怨:
main.cpp: In function 'int main(int, char**)':
main.cpp:16:69: error: conversion from 'std::_Bind_helper<false, void (*)(int, float, const std::__cxx11::basic_string<char>&), int, const std::_Placeholder<1>&, const std::_Placeholder<2>&>::type {aka std::_Bind<void (*(int, std::_Placeholder<1>, std::_Placeholder<2>))(int, float, const std::__cxx11::basic_string<char>&)>}' to non-scalar type 'std::function<void(int, float, const std::__cxx11::basic_string<char>&)>' requested
std::function<void(int, float, std::string const&)> fun = std::bind(&function, 10, std::placeholders::_1, std::placeholders::_2);
~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
请问,有人可以解释一下吗?我该如何修复这个错误?
a
绑定到10
,剩下的就只有void(float, std::string const&)
了。 - Quentinstd::bind
在C++17中已被弃用,使用lambda更受欢迎。auto fun = [](float a, std::string const& b) { function(10, a, b); };
- Zeregesstd::bind
并没有被废弃。std::bind1st
等已经被废弃,但是std::bind
仍然有一些用途:http://www.sdowney.org/2017/06/why-stdbind-cant-be-formally-deprecated/ - Alan Birtles