基类中的静态变量是否由所有派生类共享? [英] Are static variables in a base class shared by all derived classes?

问题描述

如果我有类似的东西

class Base {
    static int staticVar;
}

class DerivedA : public Base {}
class DerivedB : public Base {}

DerivedA 和 DerivedB 会共享相同的 staticVar 还是它们各自有自己的?

Will both DerivedA and DerivedB share the same staticVar or will they each get their own?

如果我想让他们每个人都有自己的，你会推荐我做什么?

If I wanted them to each have their own, what would you recommend I do?

推荐答案

它们将共享相同的 staticVar 实例.

They will each share the same instance of staticVar.

为了让每个派生类获得自己的静态变量，您需要声明另一个具有不同名称的静态变量.

In order for each derived class to get their own static variable, you'll need to declare another static variable with a different name.

然后，您可以在基类中使用一对虚拟函数来获取和设置变量的值，并在每个派生类中覆盖该对以获取和设置该类的本地"静态变量.或者，您可以使用返回引用的单个函数:

You could then use a virtual pair of functions in your base class to get and set the value of the variable, and override that pair in each of your derived classes to get and set the "local" static variable for that class. Alternatively you could use a single function that returns a reference:

class Base {
    static int staticVarInst;
public:
    virtual int &staticVar() { return staticVarInst; }
}
class Derived: public Base {
    static int derivedStaticVarInst;
public:
    virtual int &staticVar() { return derivedStaticVarInst; }
}

然后您可以将其用作:

staticVar() = 5;
cout << staticVar();

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