QMutexLocker 類

The QMutexLocker class is a convenience class that simplifies locking and unlocking mutexes. 更多...

頭：	#include <QMutexLocker>
qmake:	QT += core

所有成員列錶，包括繼承成員

注意： 此類的所有函數綫程安全 .

公共函數

	QMutexLocker (QMutex * mutex )
	~QMutexLocker ()
QMutex *	mutex () const
void	relock ()
void	unlock ()

詳細描述

The QMutexLocker class is a convenience class that simplifies locking and unlocking mutexes.

鎖定和解鎖 QMutex in complex functions and statements or in exception handling code is error-prone and difficult to debug. QMutexLocker can be used in such situations to ensure that the state of the mutex is always well-defined.

QMutexLocker should be created within a function where a QMutex needs to be locked. The mutex is locked when QMutexLocker is created. You can unlock and relock the mutex with unlock() and relock() . If locked, the mutex will be unlocked when the QMutexLocker 被銷毀。

例如，此復雜函數鎖定 QMutex 當進入函數時並在所有退齣點解鎖互斥：

int complexFunction(int flag)
{
    mutex.lock();
    int retVal = 0;
    switch (flag) {
    case 0:
    case 1:
        retVal = moreComplexFunction(flag);
        break;
    case 2:
        {
            int status = anotherFunction();
            if (status < 0) {
                mutex.unlock();
                return -2;
            }
            retVal = status + flag;
        }
        break;
    default:
        if (flag > 10) {
            mutex.unlock();
            return -1;
        }
        break;
    }
    mutex.unlock();
    return retVal;
}

此範例函數在開發過程中將變得更復雜，從而增加瞭發生錯誤的可能性。

使用 QMutexLocker greatly simplifies the code, and makes it more readable:

int complexFunction(int flag)
{
    QMutexLocker locker(&mutex);
    int retVal = 0;
    switch (flag) {
    case 0:
    case 1:
        return moreComplexFunction(flag);
    case 2:
        {
            int status = anotherFunction();
            if (status < 0)
                return -2;
            retVal = status + flag;
        }
        break;
    default:
        if (flag > 10)
            return -1;
        break;
    }
    return retVal;
}

Now, the mutex will always be unlocked when the QMutexLocker object is destroyed (when the function returns since locker 是自動變量)。

相同原理也適用於拋齣、捕捉異常的代碼。在鎖定互斥的函數中未被捕獲的異常沒有辦法解鎖互斥，在把異常嚮上傳遞給調用函數的堆棧之前。

QMutexLocker also provides a mutex() member function that returns the mutex on which the QMutexLocker is operating. This is useful for code that needs access to the mutex, such as QWaitCondition::wait ()。例如：

class SignalWaiter
{
private:
    QMutexLocker locker;
public:
    SignalWaiter(QMutex *mutex)
        : locker(mutex)
    {
    }
    void waitForSignal()
    {
        ...
        while (!signalled)
            waitCondition.wait(locker.mutex());
        ...
    }
};

另請參閱 QReadLocker , QWriteLocker ，和 QMutex .

成員函數文檔編製

QMutexLocker:: QMutexLocker ( QMutex * mutex )

構造 QMutexLocker 和鎖 mutex . The mutex will be unlocked when the QMutexLocker 被銷毀。若 mutex 為 0， QMutexLocker 什麼都不做。

另請參閱 QMutex::lock ().

QMutexLocker:: ~QMutexLocker ()

銷毀 QMutexLocker 並解鎖在構造函數中被鎖定的互斥。

另請參閱 QMutex::unlock ().

QMutex *QMutexLocker:: mutex () const

返迴互斥在那裏 QMutexLocker 正在運轉。

void QMutexLocker:: relock ()

重新鎖定被解鎖的互斥鎖定器。

另請參閱 unlock ().

void QMutexLocker:: unlock ()

解鎖此互斥鎖定器。可以使用 relock() 以再次鎖定它。它不需要被鎖定當銷毀時。

另請參閱 relock ().