是所有派生类共享的基类中的静态变量吗？ [英] Are static variables in a base class shared by all derived classes?

问题描述

如果我有像

class Base {
	static int staticVar;
}

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

DerivedA 和 DerivedB 共享同一个

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

如果我想他们每个都有自己的，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 staticVar 的同一个实例

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，您可以使用一个返回引用的函数：

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; }
}

然后您可以使用：

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

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