三种继承方式的区别

主要区别：

• public继承时，基类的private成员对派生类不可见，基类的public成员、protected成员相应地变成派生类的public、protected成员；
• private继承时，基类的private成员对派生类不可见，基类的public成员、protected成员变成派生类的private成员；
• protected继承时，基类的private成员对派生类不可见，基类的public成员、protected成员变成派生类的protected成员。

更详细的访问权限：

访问权限测试代码：

#include <iostream>
#include <algorithm>
using namespace std;
class A{
    friend void print0(const A& a){
        cout << a.x1 << a.x2 << a.x3 << endl;
    }
public:
    int x1;
    A():x1(1), x2(2), x3(3){}
private:
    int x2;
protected:
    int x3;
};
class B: public A{
    friend void print1(const A& a){
        cout << a.x1 << endl;
        //cout << a.x2 << endl;
        //cout << a.x3 << endl;
    }
public:
    B(){
        cout << x1 << endl;
        //cout << x2 << endl;
        cout << x3 << endl;
    }
};
class C: private A{
    friend void print2(const A& a){
        cout << a.x1 << endl;
        //cout << a.x2 << endl;
        //cout << a.x3 << endl;
    }
public:
    C(){
        cout << x1 << endl;
        //cout << x2 << endl;
        cout << x3 << endl;
    }
};
class D: protected A{
    friend void print3(const A& a){
        cout << a.x1 << endl;
        //cout << a.x2 << endl;
        //cout << a.x3 << endl;
    }
public:
    D(){
        cout << x1 << endl;
        //cout << x2 << endl;
        cout << x3 << endl;
    }
};
int main()
{
    A a;
    a.x1;
    //a.x2;
    //a.x3;
    B b;
    b.x1;
    //b.x2;
    //b.x3;
    C c;
    //c.x1;
    //c.x2;
    //c.x3;
    D d;
    //d.x1;
    //d.x2;
    //d.x3;
}