Thread affinity与跨线程信号槽

 

 

QObject的线程依附性（thread affinity）是指某个对象的生命周期依附的线程（该对象生存在该线程里）。我们在任何时间都可以通过调用QObject::thread()来查询线程依附性，它适用于构建在QThread对象构造函数的对象。

 

// file multiSignal.h #ifndef MULTISIGNAL_H #define MULTISIGNAL_H #include <QThread> class Thread : public QThread { Q_OBJECT signals: void aSignal(); protected: void run(); }; class Object: public QObject { Q_OBJECT public slots: void aSlot(); }; #endif // MULTISIGNAL_H  

 

 

#include <QtCore/QCoreApplication> #include <QDebug> #include <QTimer> #include "multiSignal.h" void Object::aSlot() { QTimer *timer = new QTimer; qDebug()<< "aSlot " << timer->thread(); qDebug() << "aSlot called"; delete timer; } void Thread::run() { QTimer *timer = new QTimer; qDebug()<< "run " << timer->thread(); emit aSignal(); delete timer; } int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); Thread thread; Object obj; qDebug()<< "mainThread " << a.thread(); qDebug()<< "thread " << thread.thread(); qDebug()<< "Object " << obj.thread(); QObject::connect(&thread, SIGNAL(aSignal()), &obj, SLOT(aSlot())); thread.start(); return a.exec(); }  

 

打印结果：

 

Debugging starts

 

mainThread QThread(0x3e2870)

thread QThread(0x3e2870)

Object QThread(0x3e2870)

run Thread(0x22ff1c)

aSlot QThread(0x3e2870)

aSlot called 

 

我们知道跨线程的信号槽连接需要使用queued connection，   上述代码中QObject::connect(&thread, SIGNAL(aSignal()), &obj, SLOT(aSlot()));  虽然thread与obj的线程依附性相同，它们都隶属于 地址为0x3e2870的线程；  但是我们看到发射aSignal的线程

与之不同是0x22ff1c. 这就是为什么使用queued connection。

 

更多深入的讨论请参见我即将翻译完稿的文章 事件循环与线程二