QT与DoNet中单例模式的简单实现

由于使用场景的不同，单例模式的写法也有所区别。

目前接触到的，大多数都是多线程，大量数据处理，还要考虑灵活性，对原有类结构改动最小等因素，所以写法更是多种多样。

QT个人较常用的一种写法：（两个文件：分为.h文件和.cpp文件）

class LocalBusiness : public QObject
{
    Q_OBJECT

private:
    QString _myName;
    explicit LocalBusiness(QObject *parent = nullptr);
    static LocalBusiness* _instance;
public:
    static LocalBusiness* Instance()
    {
        static QMutex mutex;
        if (!_instance) {
            QMutexLocker locker(&mutex);
            if (!_instance) {
                _instance = new LocalBusiness;
            }
        }
        return _instance;
    }
public:
    void SayHello();

};

LocalBusiness* LocalBusiness::_instance = nullptr;

LocalBusiness::LocalBusiness(QObject *parent) : QObject(parent)
{
    _myName="LocalBusiness";
}

void LocalBusiness::SayHello()
{
    qDebug() << "hello,"+_myName;
}

具体调用

    LocalBusiness::Instance()->SayHello();

C#个人较常用的写法：（一个文件：.cs文件）

    public class LocalBusiness
    {
        private readonly string _myName = string.Empty;
        private static LocalBusiness _instance = null;
        private static readonly object _locker = new object();

        private LocalBusiness()
        {
            _myName = "LocalBusiness";
        }

        public static LocalBusiness Instance
        {
            get
            {
                if (_instance == null)
                {
                    lock (_locker)
                    {
                        if (_instance == null)
                        {
                            _instance = new LocalBusiness();
                        }
                    }
                }
                return _instance;
            }
        }

        public void SayHello()
        {
            Console.WriteLine("hello,"+ _myName);
        }
    }

具体调用

            LocalBusiness.Instance.SayHello();

如果有帮助，欢迎素质三连~