boost::bind 与 boost::function 的使用方法例子

啥也不说，直接看代码：

#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <iostream>

using namespace boost;
using namespace std;

int f(int a, int b)
{
    return a + b;
}

int g(int a, int b, int c)
{
    return a + b * c;
}

class Point
{
public:
    Point(int x, int y) : _x(x), _y(y) {}
    void print(const char *msg) {
        cout << msg << "x=" << _x << ", y=" << _y << endl;
    }
private:
    int _x, _y;
};

int main()
{
    //! f 有多少个参数，f 后面就要跟多少个参数。如果不明确的，用占位符
    cout << bind(f, 2, 3)() << endl;    // ==> f(2, 3)
    cout << bind(f, 12, _1) (5) << endl;   // ==> f(12, 5)，其中参数b为不明确参数
    cout << bind(g, _2, _1, 3) (3, 5) << endl;  // ==> g(5, 3, 3) 注意顺序

    Point p(11, 34);
    Point &rp = p;
    Point *pp = &p;

    bind(&Point::print, p, "Point: ") ();
    //   ^              ^
    // 注意，为表示Point::print为成员函数，成员函数前面要加&区分。
    // 对象可以为实例、引用、指针
    bind(&Point::print, rp, "Reference: ") ();  //! 引用
    bind(&Point::print, pp, _1) ("Pointer: ");  //! 指针
    bind(&Point::print, _1, _2) (p, "As parameter: ");  //! 对象也可以用占位符暂时代替

    //! function的类型定义与需要的参数有关
    function<void ()> func0 = bind(&Point::print, p, "func0: ");
    function<void (const char *)> func1 = bind(&Point::print, pp, _1);

    func0();    //! function对象的调用
    func1("func1: ");

    return 0;
}

一般情况下，bind 与 function 配合使用。

bind与function还可以将类型完成不同的函数（成员函数与非成员函数）包装成统一的函数调用接口。如下示例：

#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <iostream>
#include <vector>

using namespace boost;
using namespace std;

class Point
{
public:
    Point(int x, int y) : _x(x), _y(y) {}
    void print(string msg) {
        cout << msg << "x=" << _x << ", y=" << _y << endl;
    }
private:
    int _x, _y;
};

class Person
{
public:
    Person(string name, int age) : _name(name), _age(age) {}
    void sayHello() {
        cout << "Hello, my name is " << _name << ", my age is : " << _age << endl;
    }
private:
    string _name;
    int _age;
};

void printSum(int limit)
{
    int sum = 0;
    for (int i = 0; i < limit; ++i) {
        sum += i;
    }
    cout << "sum = " << sum << endl;
}

void doAll(vector<function<void ()> > &funcs)
{
    for (size_t i = 0; i < funcs.size(); ++i) {
        funcs[i] ();
    }
}

int main()
{
    vector<function<void ()> > funcList;

    Person john("John", 23);
    funcList.push_back(bind(&Person::sayHello, john));

    Point p1(23, 19);
    funcList.push_back(bind(&Point::print, p1, "Point: "));

    funcList.push_back(bind(printSum, 20));

    doAll(funcList);
    return 0;
}