Qt中使用单例getInstance()示例 （含自动释放方法）

单例的实现方法：

class Helper : public QObject
{
private:
    explicit Helper(QObject *parent = 0);
    static Helper *_instance;

public:
    static Helper *getInstance()
    {
        static QMutex mutex;
        if (!_instance)
        {
            QMutexLocker locker(&mutex);
            if (!_instance)
            {
                _instance = new Helper;
            }
        }
        return _instance;
    }

    void process(void);
};class Helper : public QObject