c# - 如何在 C# 中不提供全局/静态变量的情况下实现单例模式？

Question

可能重复：
如何在不使用静态/全局变量的情况下实现单例？可能的？

大多数人说 Singleton 是邪恶的原因之一是它提供了一个全局访问点，或者它变得像一个全局变量。是否可以在没有任何类型的全局变量（包括静态变量）的情况下实现单例。是否可以在 C#.NET 中执行此操作？

Answer 1

The problem you are hinting at is that a Singleton becomes like a global var. What it uses is irrelevant.

And the answer would be No. You will always need a static somewhere, you can only defer it. And that kind of defeats the point.

Answer 2

不，那不会是单身人士。

您可以使用 IoC 容器仅将事物作为单例注入。

Answer 3

You could implement an interface and then use something like StructureMap. In SM you would build the class like this:

public class Foo : IFoo
{
}

And then you would define, in your container, the following:

ObjectFactory.Initialize(x =>
{
    x.For<IFoo>.Singleton().Use<Foo>();
}

Then you would inject this resource where you needed it:

public class Bar
{
    public Bar(IFoo foo)
    {
    }
}

So, now there will only ever be one instance of the concrete created and then injected into an enumerable number of types that need it.

Answer 4

我不相信。如果没有静态变量，您将实例存储在哪里？通常，当我想要一个类的单例时，我将所有构造函数设为私有，并提供一个静态方法或属性，如果它尚未创建，它将创建实例，并返回实例。实例本身存储为私有变量，因此访问它的唯一方法是通过提供的方法/属性 - 或反射。