QT之使用QMutex/ QMutexLocker互斥量同步线程小例子

    接上一篇，在多线程中基本上都需要解决线程同步问题，本篇文章主要将介绍如何使用QMutex/ QMutexLocker互斥量来同步线程。

    首先，先回顾下Qt官网QThreads general usage介绍，其中有一段基本上介绍了其使用方法，如下：

    The main thing in this example to keep in mind when using a QThread is that it's not a thread. It's a wrapper around a thread object. This wrapper provides the signals, slots and methods to easily use the thread object within a Qt project. To use it, prepare a QObject subclass with all your desired functionality in it. Then create a new QThread instance, push the QObject onto it using moveToThread(QThread*) of the QObject instance and call start() on the QThread instance. That's all. You set up the proper signal/slot connections to make it quit properly and such, and that's all.

    现在，直接上售票的小例子：

    Step1. 按Qt介绍的用法：先创建一个继承QObject的类，把要执行的函数包装进里面：

.h 文件代码如下：

#ifndef TICKETSELLER_H
#define TICKETSELLER_H

#include 
#include 
#include 
#include 

class TicketSeller : public QObject
{
public:
    TicketSeller();

    ~TicketSeller();

public slots:
    void sale();

public:
    int* tickets;

    QMutex* mutex;

    std::string name;
};

#endif // TICKETSELLER_H

.cpp 文件代码如下：

#include "ticketseller.h"
#include 

TicketSeller::TicketSeller()
{
    tickets = 0;
    mutex = NULL;
}

TicketSeller::~TicketSeller()
{

}

void TicketSeller::sale()
{
    while((*tickets) > 0)
    {
        mutex->lock();
        std::cout << name << " : " << (*tickets)-- << std::endl;
        mutex->unlock();
    }

    /*while((*tickets) > 0)
    {
        QMutexLocker locker(mutex);
        std::cout << name << " : " << (*tickets)-- << std::endl;
        locker.unlock();
    }*/
}

    Step2. 按Qt介绍的用法：创建一个实例，使用moveToThread将对象移至QThread内，并连接信号槽，最后调用start()方法：

main.cpp 文件代码如下：

#include 
#include 
#include 
#include 
#include "ticketseller.h"

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);   

    int ticket = 100;
    QMutex mutex;

    /*创建设置线程1*/
    //创建线程1
    QThread t1;
    TicketSeller seller1;
    //设置线程1
    seller1.tickets = &ticket;
    seller1.mutex = &mutex;
    seller1.name = "seller1";
    //将对象移动到线程
    seller1.moveToThread(&t1);

    /*创建设置线程2*/
    //创建线程2
    QThread t2;
    TicketSeller seller2;
    seller2.tickets = &ticket;
    seller2.mutex = &mutex;
    seller2.name = "seller2";
    //将对象移动到线程
    seller2.moveToThread(&t2);

    QObject::connect(&t1, &QThread::started, &seller1, &TicketSeller::sale);
    QObject::connect(&t2, &QThread::started, &seller2, &TicketSeller::sale);

    t1.start();
    t2.start();

    return a.exec();
}

    QT 中使用 QMutex/ QMutexLocker 比Window API CreateMutex 配合 WaitForSingleObject 同步线程要简单得多。