boost库 bind/function的使用

柔情只为你懂 2022-08-13 14:46 181阅读 0赞

Boost::Function 是对函数指针的对象化封装，在概念上与广义上的回调函数类似。相对于函数指针，function除了使用自由函数，还可以使用函数对象，甚至是类的成员函数，这个就很强大了哈

#include <boost/function.hpp>
    #include <boost/bind.hpp>
    #include <iostream>
     
    using namespace std;
     
     
    class TestA
    {
        public:
            void method()
            {
                cout<<"TestA: method: no arguments"<<endl;
            }
     
            void method(int a, int b)
            {
                cout<<"TestA: method: with arguments"
                    <<"value of a is:"<<a 
                    <<"value of b is "<<b <<endl;
            }
    };
     
     
    void sum(int a, int b)
    {
        int sum = a + b;
        cout<<"sum: "<<sum<<endl;
    } 
     
    int main()
    {
        boost::function<void()> f;
        TestA test;
     
        f = boost::bind(&TestA::method, &test);
        f();
     
        f = boost::bind(&TestA::method, &test, 1, 2);
        f();
     
        f = boost::bind(&sum, 1, 2);
        f();
    }

### 2. 应用：Thread封装 ###

在实现自定义的线程类时，曾经这么干过：定义虚函数run()，用户自定义的CustomThread::Thread后，自己实现run()函数就OK了。 当时觉得这么做也不错。  
现在有了boost::function/boost::bind我们可以这么干：  
定义一个线程类：  
.h文件

#include <pthread.h>
    #include <string>
    #include <boost/function.hpp>
    #include <boost/bind.hpp>
     
    using namespace std;
    class Thread
    {
        typedef boost::function<void()> ThreadFun;
        public:
            Thread(const ThreadFun& threadFun,const string& threadName = string());
            pid_t     getThreadId();
            string    getThreadName();
            int       start();
         
        private:
            static void* startThread(void* thread);
       
        private:
            pthread_t   m_thread; //线程句柄
            pid_t       m_tid;    //线程ID
            string      m_strThreadName;    //线程名称
            bool        m_bStarted;         //线程是否启动
            ThreadFun   m_func;             //线程处理函数
    };

.cpp

#include "thread.h"
     
    Thread::Thread(const Thread::ThreadFun& threadFun, const string& threadName):
    m_func(threadFun), m_strThreadName(threadName)
    {
    }
     
    int Thread::start()
    {
        m_tid = pthread_create(&m_thread, NULL, &startThread, this);
        return 0;
    }
     
    void* Thread::startThread(void* obj)
    {
      Thread* thread = static_cast<Thread*>(obj);
      thread->m_func();
      return NULL;
    }
     
    pid_t Thread::getThreadId()
    {
        return m_tid;
    };
     
    string  Thread::getThreadName()
    {
        return m_strThreadName;
    }

void ThreadProcess()
    {
        int count = 100;
        for (int i = 0; i < count; i++)
        {
            if (i % 10 == 0)    
            cout<<"\n";
            cout<<i<<"\t";
        }
    }
     
    int main()
    {
        boost::function<void()> f;
        f = boost::bind(&ThreadProcess);    
            Thread thread(f, "ThreadTest");
            thread.start();
        sleep(1000*1000);
        return 0;
    }