3.单例模式.ipynb

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    "# 单例模式 Singleton Pattern\n",
    "\n",
    "单例类在整个系统中只能有一个实例，应该自己创建这个唯一的实例并且为其他对象提供。"
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    "#nullable enable\n",
    "\n",
    "public class Singleton{\n",
    "    private static Singleton? _instance;\n",
    "    private static object _lock = new object();\n",
    "    protected Singleton(){}\n",
    "    public static Singleton Instance{\n",
    "        get {\n",
    "            //使用了double check提高效率\n",
    "            if(_instance == null){\n",
    "                //加锁保证线程安全\n",
    "                lock(_lock){\n",
    "                    if(_instance == null){\n",
    "                        _instance =  new Singleton();\n",
    "                    }\n",
    "                }\n",
    "            }\n",
    "            return _instance;\n",
    "        }\n",
    "    }\n",
    "    public void Work(){\n",
    "        Console.WriteLine(\"Singleton works!\");\n",
    "    }\n",
    "}\n",
    "\n",
    "Singleton.Instance.Work();"
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    "另一种实现方式：\n",
    "用private限制构造函数的访问，利用static readonly在程序初始化时就被实例化，保证在使用过程中不会被修改。\n",
    "缺点是没有延迟初始化，会影响程序启动速度。"
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   "source": [
    "public class Singleton{\n",
    "    private Singleton(){}\n",
    "    public static readonly Singleton Instance = new Singleton();\n",
    "    public void Work(){\n",
    "        Console.WriteLine(\"Singleton works!\");\n",
    "    }\n",
    "\n",
    "}\n",
    "\n",
    "Singleton.Instance.Work();"
   ]
  }
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