辛格尔顿与参数 [英] Singleton with parameters

问题描述

我需要一个单独的类与一些参数进行实例化。我现在做的方式是：

I need a singleton class to be instantiated with some arguments. The way I'm doing it now is:

class SingletonExample
{
     private SingletonExample mInstance;
     //other members... 
     private SingletonExample()
     {

     } 
     public SingletonExample Instance
     {
         get
         {
              if (mInstance == null)
              {
                  throw new Exception("Object not created");
              }
              return mInstance;
         }
     }

     public void Create(string arg1, string arg2)
     {
         mInstance = new SingletonExample();
         mInstance.Arg1 = arg1;
         mInstance.ObjectCaller = new ObjectCaller(arg2);
         //etc... basically, create object...
     } 
}

实例被创建晚，这意味着我没有所有的需要的参数上的应用程序启动。

The instance is created 'late', meaning I don't have all of the needed arguments on app startup.

在一般我不喜欢强迫方法调用的顺序，但我没有看到这里的另一种方式。 IOC将于不能解决，要么，因为在那里我可以在容器中进行注册，我也可以调用Create（）...

In general I don't like forcing an ordering of method calls, but I don't see another way here. The IoC wouldn't resolve it either, since where I can register it in the container, I can also call Create()...

你认为这是一个好方案？你有一些其他的想法？

Do you consider this an OK scenario? Do you have some other idea?

修改：我的知道我写的，因为它不是线程安全的一个例子，线程安全的是的不是问题的一部分。

edit: I know that what I wrote as an example it's not thread safe, thread-safe isn't part of the question

推荐答案

带有参数的辛格尔顿腥的气味给我。

A Singleton with parameters smells fishy to me.

考虑whateva的答案，以下code：

Consider whateva's answer and the following code:

Singleton x = Singleton.getInstance("hello", "world");
Singleton y = Singleton.getInstance("foo", "bar");

显然，X == y和y的作品与X的创建参数，而在Y的创建参数被忽略。结果可能是......混乱最少。

Obviously, x==y and y works with x's creation parameters, while y's creation parameters are simply ignored. Results are probably... confusing at least.

如果你真的喜欢下跌，你必须这样做，这样做是这样的：

If you really, really fell like you have to do it, do it like this:

class SingletonExample
{
     private static SingletonExample mInstance;
     //other members... 
     private SingletonExample()
     {  // never used
        throw new Exception("WTF, who called this constructor?!?");
     }
     private SingletonExample(string arg1, string arg2)
     {
         mInstance.Arg1 = arg1;
         mInstance.ObjectCaller = new ObjectCaller(arg2);
         //etc... basically, create object...    
     } 
     public static SingletonExample Instance
     {
         get
         {
              if (mInstance == null)
              {
                  throw new Exception("Object not created");
              }
              return mInstance;
         }
     }

     public static void Create(string arg1, string arg2)
     {
         if (mInstance != null)
         {
             throw new Exception("Object already created");
         }
         mInstance = new SingletonExample(arg1, arg2);             
     } 
}

在多线程环境中，添加同步，以避免竞争条件。

In a multithreading environment, add synchronisation to avoid race conditions.

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