在C ++中防止类继承 [英] Prevent class inheritance in C++

问题描述

我最近的一个朋友问我如何在C ++中防止类继承。他希望编辑失败。

我在想，并找到3个答案。

pre> class CBase
{

public：

static CBase * CreateInstance（）
{
CBase * b1 = new CBase（）;
return b1;
}

private：

CBase（）{}
CBase（CBase3）{}
CBase& operator =（CBase&）{}


};


2）使用CSealed base class，private ctor&虚拟继承

  class CSealed 
 {
 
 private：
 
 CSealed（）{
} 
 
朋友类CBase; 
}; 
 
 
 class CBase：virtual CSealed 
 {
 
 public：
 
 CBase（）{
} 
 
}; 
  

3）使用CSealed基类，protected ctor&虚拟继承

  class CSealed 
 {
 
 protected：
 
 CSealed（）{
} 
 
}; 
 
 class CBase：virtual CSealed 
 {
 
 public：
 
 CBase（）{
} 
 
}; 
  

所有上述方法确保CBase类不能继承。
我的问题是：

1）哪个是最好的方法？还有其他方法吗？

2）方法2& 3将不工作，除非CSealed类继承为virutally。这是为什么 ？它与vdisp ptr有什么关系？

PS：

上面的程序是在MS C ++编译器（Visual Studio）。
reference： http://www.codeguru.com/forum/archive/ index.php / t-321146.html

解决方案

从C ++ 11开始，例如

  class CBase final 
 {
 ... 
  

我可以看到的主要原因是想做这件事（我找到这个问题的原因）类作为非子类，因此您可以安全地使用非虚拟析构函数，并完全避免vtable。

Recently one of my friend asked me how to prevent class inheritance in C++. He wanted the compilation to fail.

I was thinking about it and found 3 answers. Not sure which is the best one.

1) Private Constructor(s)

class CBase
{

public:

 static CBase* CreateInstance() 
 { 
  CBase* b1 = new CBase();
  return b1;
 }

private:

 CBase() { }
 CBase(CBase3) { }
 CBase& operator=(CBase&) { }


};

2) Using CSealed base class, private ctor & virtual inheritance

class CSealed
{

private:

 CSealed() {
 }

 friend class CBase;
};


class CBase : virtual CSealed
{

public:

 CBase() {
 }

};

3) Using a CSealed base class, protected ctor & virtual inheritance

class CSealed
{

protected:

 CSealed() {
 }

};

class CBase : virtual CSealed
{

public:

 CBase() {
 }

};

All the above methods make sure that CBase class cannot be inherited further. My Question is:

1) Which is the best method ? Any other methods available ?

2) Method 2 & 3 will not work unless the CSealed class is inherited virutally. Why is that ? Does it have anything to do with vdisp ptr ??

PS:

The above program was compiled in MS C++ compiler (Visual Studio). reference : http://www.codeguru.com/forum/archive/index.php/t-321146.html

解决方案

As of C++11, you can add the final keyword to your class, eg

class CBase final
{
...

The main reason I can see for wanting to do this (and the reason I came looking for this question) is to mark a class as non subclassable so you can safely use a non-virtual destructor and avoid a vtable altogether.

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