(7条消息) C++11 std::bind std::function 高级用法 / 四六文摘

从最基础的了解，std::bind和std::function

/*
* File: main.cpp
* Author: Vicky.H
* Email: eclipser@163.com
*/
#include <iostream>
#include <functional>
#include <typeinfo>
#include <string.h>
int add1(int i, int j, int k) {
return i + j + k;
}
class Utils {
public:
Utils(const char* name) {
strcpy(_name, name);
}
void sayHello(const char* name) const {
std::cout << _name << " say: hello " << name << std::endl;
}
static int getId() {
return 10001;
}
int operator()(int i, int j, int k) const {
return i + j + k;
}
private:
char _name[32];
};
/*
*
*/
int main(void) {
// 绑定全局函数
auto add2 = std::bind(add1, std::placeholders::_1, std::placeholders::_2, 10);
// 函数add2 = 绑定add1函数，参数1不变，参数2不变，参数3固定为10.
std::cout << typeid(add2).name() << std::endl;
std::cout << "add2(1,2) = " << add2(1, 2) << std::endl;
std::cout << "\n---------------------------" << std::endl;
// 绑定成员函数
Utils utils("Vicky");
auto sayHello = std::bind(&Utils::sayHello, utils/*调用者*/, std::placeholders::_1/*参数1*/);
sayHello("Jack");
auto sayHelloToLucy = std::bind(&Utils::sayHello, utils/*调用者*/, "Lucy"/*固定参数1*/);
sayHelloToLucy();
// 绑定静态成员函数
auto getId = std::bind(&Utils::getId);
std::cout << getId() << std::endl;
std::cout << "\n---------------------------" << std::endl;
// 绑定operator函数
auto add100 = std::bind(&Utils::operator (), utils, std::placeholders::_1, std::placeholders::_2, 100);
std::cout << "add100(1, 2) = " << add100(1, 2) << std::endl;
// 注意：无法使用std::bind()绑定一个重载函数
return 0;
}

/*
* File: main2.cpp
* Author: Vicky.H
* Email: eclipser@163.com
*/
#include <iostream>
#include <typeinfo>
void sayHello() {
std::cout << "Hello world !" << std::endl;
}
int sum(int i, int j, int k) {
return i + j + k;
}
template <typename T>
class Func {
public:
Func(T fun) {
if (!fun) {
throw "fun nullptr";
}
_fun = fun;
}
template<typename R, typename A1, typename A2, typename A3, typename A4, typename A5>
R Call(A1 a1, A2 a2, A3 a3, A4 a4, A5 a5) {
return _fun(a1, a2, a3, a4, a5);
}
template<typename R, typename A1, typename A2, typename A3, typename A4>
R Call(A1 a1, A2 a2, A3 a3, A4 a4) {
return _fun(a1, a2, a3, a4);
}
template<typename R, typename A1, typename A2, typename A3>
R Call(A1 a1, A2 a2, A3 a3) {
return _fun(a1, a2, a3);
}
template<typename R, typename A1, typename A2>
R Call(A1 a1, A2 a2) {
return _fun(a1, a2);
}
template<typename R, typename A1>
R Call(A1 a1) {
return _fun(a1);
}
template<typename R>
R Call() {
return _fun();
}
void Call() {
_fun();
}
private:
T _fun;
};
#include <functional>
template<typename R = void, typename... Args>
class Fn {
public:
Fn(std::function<R(Args...)> fun) : _fun(fun) {
}
R operator()(Args... args) {
return _fun(args...);
}
private:
std::function<R(Args...) > _fun;
};
/*
* 将函数注册到对象中，通过对象直接调用
*/
int main(void) {
Func<void(*)() > sayHelloFunc(sayHello);
sayHelloFunc.Call();
Func<int (*)(int, int, int) > sumFunc(sum);
std::cout << "sumFunc.Call<int>(1, 2, 3) : " << sumFunc.Call<int>(1, 2, 3) << std::endl;
std::cout << "\n---------------------------" << std::endl;
Fn<> sayHelloFn(sayHello);
sayHelloFn();
Fn<int, int, int, int> sumFn(sum);
std::cout << "sumFn(1, 2, 3) : " << sumFn(1, 2, 3) << std::endl;
std::cout << "\n---------------------------" << std::endl;
return 0;
}

Hello world ! sumFunc.Call<int>(1, 2, 3) : 6


---------------------------

Hello world !

sumFn(1, 2, 3) : 6

---------------------------

上面的例子非常有趣，使用了2种方案，将一个函数，注册到一个对象/仿函数中，并且通过一个对象/仿函数来直接调用调用。例子显而易见的，第2种方案更佳简洁，并且对传递参数有明确的判断，当参数类型或数量不正确的时候，编译器将导致失败。这种方案，可以将类的成员变量直接作为函数的参数使用，或者，如我： http://blog.csdn.net/eclipser1987/article/details/23926395 这篇文章中，无法直接调用脚本函数类，有了好的解决办法。这个我将随后补充。

#include <list>
#include <functional>
template<typename... Args>
class Fns
{
private:
std::list<std::function<void(Args...)> > _calls;
public:
virtual ~Fns()
{
_calls.clear();
}
void connect(std::function<void(Args...)> fct)
{
_calls.push_back(fct);
}
template<typename Object>
void connect(Object* object, void (Object::*method)(Args...))
{
_calls.push_back([object,method](Args... args){(*object.*method)(args...);});
}
template<typename Object>
void connect(Object* object, void (Object::*method)(Args...) const)
{
_calls.push_back([object,method](Args... args){(*object.*method)(args...);});
}
template<typename Object>
void connect(const Object* object, void (Object::*method)(Args...) const)
{
_calls.push_back([object,method](Args... args){(*object.*method)(args...);});
}
void emit(Args... args)
{
for(auto call : _calls)
call(args...);
}
};

#include <cstdio>
#include "Signal.hpp"
class Foo
{
public:
void bar(int x, int y)
{
printf("Foo::bar(%d, %d)\n", x, y);
}
};
void foobar(int x, int y)
{
printf("foobar(%d, %d)\n", x, y);
}
int main(void)
{
Foo foo;
Fns<int, int> s;
// Connect a function
s.connect(foobar);
// Connect a class method
s.connect(&foo, &Foo::bar);
// Create and connect some lambda expression
s.connect([&foo](int x, int y){
printf("lambda::"); foo.bar(x, y);
});
// Emit the signal !
s.emit(4, 2);
getchar();
return 0;
}

foobar(4, 2) Foo::bar(4, 2) lambda::Foo::bar(4, 2)

(7条消息) C++11 std::bind std::function 高级用法

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