受保护的成员与重载运算符发生冲突 [英] Protected member conflict with overloading operator

问题描述

我有以下课程：

class Base {
protected:
    int myint;        
};

class Derived : public Base {
public:
    bool operator==(Base &obj) {
        if(myint == obj.myint)
            return true;
        else
            return false;
    }
};

但是当我编译它时，会出现以下错误：

But when I compile it, it gives the following errors:

int Base :: myint 在此上下文中受保护

我认为可以在公共继承下从派生类访问受保护的变量。造成此错误的原因是什么？

I thought that protected variables are accessible from the derived class under a public inheritance. What is causing this error?

推荐答案

派生可以访问受保护的成员仅在所有派生的实例上，基本。但是 obj 不是 Derived 的实例，它是 Base -因此禁止访问。由于现在 obj 是 Derived

Derived can access protected members of Base on all instances of Derived only. But obj isn't an instance of Derived, it's an instance of Base - so access is forbidden. The following would compile fine, since now obj is a Derived

class Derived : public Base {
public:
    bool operator==(const Derived& obj) const {
        return myint == obj.myint;
    }
};

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