静态变量如何保留递增的值 [英] How static variable can retain incremented value

问题描述

我在类中创建了一个静态变量并在构造函数中递增，认为无论何时我向类创建实例，静态变量都将重置为0.令我惊讶的是，第一次创建对象时对于类，静态变量（Counter）递增为1.第二次将对象创建到类时，静态变量保留递增的值（1）。这是静态的行为吗？



我尝试过：

I created a static variable in a class and incrementing in the constructor, thinking that whenever I created an instance to the class, the static variable will be reset to 0. To my utter surprise, the first time when I created the object to the class, static variable(Counter) is incremented to 1. The second time when I created the object to the class, the static variable is retaining the incremented value(1). Is this the behavior of static?

What I have tried:

class Singleton
   {
       private static int counter = 0;
       Public Singleton()
       {
           counter++;
           Console.WriteLine("Counter-" + counter);
       }
   }

  static void Main(string[] args)
       {
           Singleton objSingleton = Singleton.getInstanse;
           objSingleton.getMessage("Hi This is my first message!");
           Singleton objSingleton2 = Singleton.getInstanse;
           objSingleton.getMessage("Hi This is my second message!");
       }

推荐答案

这不是你的代码：我可以说出两个原因。
1）它不会编译 - C＃区分大小写， Public 与 public

2）您显示的 Singleton 类不包含 getInstanse 方法，这对你的问题至关重要。



单例类的整个想法是系统中只有一个类的实例 - 所以构造函数始终声明为 private ，而不是 public ，因此它只能在类本身内创建。通常情况下，这将在 GetInstance 方法或类似方法中，但实例将保留在私有静态变量中。 class：



That isn't your code: I can tell for two reasons.
1) It won't compile - C# is case sensitive, and Public is not the same as public
2) Your Singleton class as shown doesn't contain a getInstanse method, which is crucial to your problem.

The whole idea of a singleton class is that there is one and only one instance of the class in the system - so the constructor is always declared as private, not public so it can only be created inside the class itself. Normally that would be in a GetInstance method or similar, but the instance would be retained in a private static variable inside the class:

class Singleton
    {
    private static int counter = 0;
    private static Singleton instance = null;
    private Singleton()
        {
        counter++;
        Console.WriteLine("Counter-" + counter);
        }
    public void getMessage(string s)
        {
        Console.WriteLine(s);
        }
    public static Singleton GetInstance()
        {
        if (instance == null) instance = new Singleton();
        return instance;
        }
    }

class Program
    {
    static void Main(string[] args)
        {
        Singleton objSingleton = Singleton.GetInstance();
        objSingleton.getMessage("Hi This is my first message!");
        Singleton objSingleton2 = Singleton.GetInstance();
        objSingleton.getMessage("Hi This is my second message!");

        Console.ReadLine();
        }
    }

这就是为什么你只得到1的计数器：只创建一个实例。

And that's why you only ever get a counter of 1: only one instance is ever created.

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