C++11并发学习之二：线程管理

来源：互联网发布：sql查询字段最大长度编辑：程序博客网时间：2024/05/16 01:25

1.启动线程

(1)使用对象

“小试牛刀”中thread构造时传入的是函数，还可以传入对象。

#include <thread>#include <iostream>void func(){    std::cout<<"worker thread ID:"<<std::this_thread::get_id()<<std::endl;    std::cout<<"Hello Word"<<std::endl;}class MyFunc{public:    //重载的函数操作符,对象使用起来就像对象是一个函数一样    void operator()()//无参数无返回值    {        func();    }};int main(){    std::cout<<"main thread ID:"<<std::this_thread::get_id()<<std::endl;    MyFunc myFunc;//需先定义类的对象    std::thread workerThread(myFunc);    workerThread.join();    return 0;}

(2)使用参数

#include <thread>#include <iostream>#include <string>void func(int i,std::string const &s){    std::cout<<"worker thread ID:"<<std::this_thread::get_id()<<std::endl;    std::cout<<"Hello Word"<<" "<<s<<" "<<i<<std::endl;}int main(){    std::cout<<"main thread ID:"<<std::this_thread::get_id()<<std::endl;    std::string str="at";    //注意这里第二个参数的写法    //为何不直接传str:虽然函数func的第二个参数期待传入一个引用，但是std::thread得构造函数    //并不知晓；构造函数无视函数期待的数据类型，并盲目的拷贝已提供的变量。当线程调用func函数    //时，传递给函数的参数是str变量内部拷贝的引用，而非数据本身的引用。使用std::ref可以解决    //这个问题，将参数转换成引用的形式。    std::thread workerThread(func,20161016,std::ref(str));    workerThread.join();    return 0;}

(3)使用move

#include <thread>#include <iostream>#include <string>void func(int i,std::string const &s){    std::cout<<"worker thread ID:"<<std::this_thread::get_id()<<std::endl;    std::cout<<"Hello Word"<<" "<<s<<" "<<i<<std::endl;}void func_other(int i,std::string const &s){    std::cout<<"worker thread ID:"<<std::this_thread::get_id()<<std::endl;    std::cout<<"C++11"<<" "<<s<<" "<<i<<std::endl;}int main(){    std::cout<<"main thread ID:"<<std::this_thread::get_id()<<std::endl;    std::string str="at";    std::thread workerThread1(func,20161016,std::ref(str));    std::thread workerThread2=std::move(workerThread1);    workerThread1=std::thread(func_other,20161016,std::ref(str));    std::thread workerThread3;    std::thread workerThread4;    //此句崩溃，workerThread4并未启动//  workerThread4.join();    workerThread3=std::move(workerThread2);    //此句崩溃，因为workerThread1已经关联一个线程//  workerThread1=std::move(workerThread3);    workerThread1.join();    //此句崩溃，因为workerThread2没有关联一个线程//  workerThread2.join();    workerThread3.join();    return 0;}

2.后台运行线程

#include <thread>#include <iostream>#include <string>#include <chrono>#include <assert.h>void func(int i,std::string const &s){    std::cout<<"worker thread ID:"<<std::this_thread::get_id()<<std::endl;    std::cout<<"Hello Word"<<" "<<s<<" "<<i<<std::endl;}int main(){    std::cout<<"main thread ID:"<<std::this_thread::get_id()<<std::endl;    std::string str="at";    std::thread workerThread(func,20161016,std::ref(str));    //使用detach()会让线程在后台运行，也就是说主线程不会等待workerThread结束。如果线程detach(),    //不可能有std::thread对象能引用它，而且不能再调用该线程的join()方法。    workerThread.detach();    //workerThread.joinable()为false    assert(!workerThread.joinable());    //延时10秒，否则然函数func函数还未执行，man函数就退出了    std::this_thread::sleep_for(std::chrono::seconds(10));    return 0;}

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