静态变量在静态方法中的基类和继承 [英] Static variables in static method in base class and inheritance

问题描述

我有这些C ++类：

  class Base 
 {
 protected：
 static int method（）
 {
 static int x = 0; 
 return x ++; 
} 
}; 
 
 A类：public Base 
 {
 
}; 
 
 class B：public Base 
 {
 
}; 
  

x 静态变量 A 和 B ，或者每个人都有自己的 x c $ c> c $ c> c $ c> c $ c> c $ c> c $ c> c $ c> > x 。一个很好的解决方法是使用 CRTP ：

 模板< class Derived> 
 class Base 
 {
 protected：
 static int method（）
 {
 static int x = 0; 
 return x ++; 
} 
}; 
 
 class A：public Base< A> {}; 
 class B：public Base< B> {}; 
  

这将创建一个不同的 Base< T>

你可能还需要一个 Baser基因来保留多态性，如Neil和Akanksh所指出的。

I have these C++ classes:

class Base
{
protected:
    static int method()
    {
        static int x = 0;
        return x++;
    }
};

class A : public Base
{

};

class B : public Base
{

};

Will the x static variable be shared among A and B, or will each one of them have it's own independent x variable (which is what I want)?

解决方案

There will only be one instance of x in the entire program. A nice work-around is to use the CRTP:

template <class Derived>
class Base
{
protected:
    static int method()
    {
        static int x = 0;
        return x++;
    }
};

class A : public Base<A> { };
class B : public Base<B> { };

This will create a different Base<T>, and therefore a distinct x, for each class that derives from it.

You may also need a "Baser" base to retain polymorphism, as Neil and Akanksh point out.

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