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）

 1 class LocalBusiness : public QObject
 2 {
 3     Q_OBJECT
 4
 5 private:
 6     QString _myName;
 7     explicit LocalBusiness(QObject *parent = nullptr);
 8     static LocalBusiness* _instance;
 9 public:
10     static LocalBusiness* Instance()
11     {
12         static QMutex mutex;
13         if (!_instance) {
14             QMutexLocker locker(&mutex);
15             if (!_instance) {
16                 _instance = new LocalBusiness;
17             }
18         }
19         return _instance;
20     }
21 public:
22     void SayHello();
23
24 };

 1 LocalBusiness* LocalBusiness::_instance = nullptr;
 2
 3 LocalBusiness::LocalBusiness(QObject *parent) : QObject(parent)
 4 {
 5     _myName="LocalBusiness";
 6 }
 7
 8 void LocalBusiness::SayHello()
 9 {
10     qDebug() << "hello,"+_myName;
11 }

具体调用

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

C#个人较常用的写法：（一个文件：.cs文件）

 1     public class LocalBusiness
 2     {
 3         private readonly string _myName = string.Empty;
 4         private static LocalBusiness _instance = null;
 5         private static readonly object _locker = new object();
 6
 7         private LocalBusiness()
 8         {
 9             _myName = "LocalBusiness";
10         }
11
12         public static LocalBusiness Instance
13         {
14             get
15             {
16                 if (_instance == null)
17                 {
18                     lock (_locker)
19                     {
20                         if (_instance == null)
21                         {
22                             _instance = new LocalBusiness();
23                         }
24                     }
25                 }
26                 return _instance;
27             }
28         }
29
30         public void SayHello()
31         {
32             Console.WriteLine("hello,"+ _myName);
33         }
34     }

具体调用

1             LocalBusiness.Instance.SayHello();

如果有帮助，欢迎素质三连~