类不能继承和实例化 [英] Class can not inherit and instantiate

问题描述

我有一个类，但我想限制不继承。所以我可以使用密封关键字和

不实例化我可以使用抽象关键字，但两个关键字一次不可用如何处理这些scnerio？

解决方案

唯一一个永远不会被你的代码直接实例化的类是一个'静态类，当然第一次有引用时，'静态类将创建。并且，你不能继承'静态类。



这符合你的要求吗？



Singleton Class将由您实例化一次;你可以标记它'密封以防止从它继承。并且，请注意，可以使用反射来调用Singleton的私有构造函数：虽然很难想象有人疯狂到想要这样做:)。



Singleton的善是它可以实现接口，可以从另一个类派生，可以在委托中传递。有些人认为单身人士是邪恶的，但是，由于他们几乎虔诚地强烈关注。



抽象类是设计的继承自;它们无法实例化，或者密封了access-modifier;他们可以从另一个类继承，包括另一个'抽象类，并且不能实现接口。



你可以疯狂地实现各种继承方案，比如这个恐怖：

  public   interface   Interface1  
 {
  string   theString  {set;得到; } 
 }  
 
  public   interface   Interface2  
 {
  int   theInteger  {set;得到; } 
 }  
 
  public   class   Class1  ：  Interface1  
 {
  public   string   theString  {set;得到; } 
 
  public  Class1（）
 {
  theString  =hello0; 
} 
 }  
 
  public   abstract   class   abstractClass1  ：  Class1 ， Interface2  
 {
  public   string   theString  {set;得到; } 
 
  public   int   theInteger  {set;得到; } 
 
  public  abstractClass1（）
 {
  theString  =hello1; 
} 
 }  
 
  public   abstract   class   abstractClass2  ：  abstractClass1  
 {
  public   string   theString  {set;得到; } 
 
  public  abstractClass2（）
 {
  theString  =hello2; 
 
  theInteger  = 108; 
} 
 }  
 
  public  类  Class3  ：  abstractClass2  
 {
  public  Class3（）
 {
  theString  =hello3; 
 
  theInteger  = 0; 
} 
 }  
 
  //  在某些方法中尝试此操作，或者在EventHandler中尝试： 
  Class3   class3   =   new  Class3（）; 
 
  string   str   =   class3  .theString; 
 
  int   i   =   class3  .theInteger; 

但是，为什么要实现这种奇怪的关系呢？

你正在寻找一个单身人士 - 这是一个过度使用的设计模式，你应该避免它，但如果你坚持：

http://csharpindepth.com/Articles/General/Singleton.aspx

I have a class but i want to restrict not to inherit.so i can use sealed keyword and
not to instantiate i can use abstract keyword but both keywords are not useable at a time how to handle these scnerio?

解决方案

The only type of Class that will never be instantiated directly by your code is a 'static Class, of course a 'static class will be created the first time there is a reference to it. And, you cannot inherit from a 'static Class.

Does that meet your requirements ?

The Singleton Class will be instantiated by you, once; you can mark it 'Sealed to prevent inheritance from it. And, note that one could use reflection to call the private constructor of a Singleton: although it's hard to imagine anybody crazy enough to want to do that :).

The "goodness" of a Singleton is that it can implement Interfaces, can be derived from another Class, could be passed in a delegate. There are those who consider Singletons as "evil," however, for reasons they are almost "religiously" intense about.

Abstract Classes are designed to be inherited from; they cannot be instantiated, or have the access-modifier 'sealed; they can inherit from another class, including another 'abstract Class, and cannot implement Interfaces.

You can drive yourself crazy implementing all kinds of inheritance scenarios, like this horror:

public interface Interface1
{
    string theString { set; get; }
}

public interface Interface2
{
    int theInteger { set; get; }
}

public class Class1 : Interface1
{
    public string theString { set; get; }

    public Class1()
    {
        theString = "hello0";
    }
}

public abstract class abstractClass1 : Class1, Interface2
{
    public string theString { set; get; }

    public int theInteger { set; get; }

    public abstractClass1()
    {
        theString = "hello1";
    }
}

public abstract class abstractClass2 : abstractClass1
{
    public string theString { set; get; }

    public abstractClass2()
    {
        theString = "hello2";

        theInteger = 108;
    }
}

public class Class3 : abstractClass2
{
    public Class3()
    {
        theString = "hello3";

        theInteger = 0;
    }
}

// try this in some method, or EventHandler:
Class3 class3 = new Class3();

string str = class3.theString;

int i = class3.theInteger;

But, why would you ever implement such strange relationships ?

You are looking for a Singleton -- it's an overused Design Pattern, and you should probably avoid it, but if you insist:
http://csharpindepth.com/Articles/General/Singleton.aspx

这篇关于类不能继承和实例化的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！