继承方式理解的作业

目标： 验证公用继承下基类的公用成员在派生类依然为公用成员

测试用程序代码：

#include <iostream>
using namespace std;

class A {
public:
	int a1 = 10;
protected:
	int a2 = 20;
public:
	virtual void dsp() {
		cout << "A : public a1 =  " << a1 << ", protected a2 =  " << a2 << endl;
	}
};


class B : public A {
public:
	int b1 = 30;
	void seta2(int i) {
		a2 = i;
	}
	void dsp() override {
		cout << "B : public a1 =  " << a1 << ", protected a2 =  " << a2 << endl;
	}
};


class C : public B {
public:
	void dsp() override {
		cout << "C : public a1 =  " << a1 << ", protected a2 =  " << a2 << ", public b1 =  " << b1 << endl;
	}

};

void Show(A& d, B& d1, C& d2) {
	d.dsp(); d1.dsp(); d2.dsp();
	cout << "----------------------" << endl;
}

int main() {
	A d;
	B d1;
	C d2;
	Show(d, d1, d2);
	d1.a1 = 100;
	Show(d, d1, d2);
	d2.a1 = 200;
	Show(d, d1, d2);
	d1.seta2(300);
	Show(d, d1, d2);
	d2.seta2(400);
	Show(d, d1, d2);
	return 0;
}

出现现象：

输出：

A : public a1 =  10, protected a2 =  20
B : public a1 =  10, protected a2 =  20
C : public a1 =  10, protected a2 =  20, public b1 =  30
----------------------
A : public a1 =  10, protected a2 =  20
B : public a1 =  100, protected a2 =  20
C : public a1 =  10, protected a2 =  20, public b1 =  30
----------------------
A : public a1 =  10, protected a2 =  20
B : public a1 =  100, protected a2 =  20
C : public a1 =  200, protected a2 =  20, public b1 =  30
----------------------
A : public a1 =  10, protected a2 =  20
B : public a1 =  100, protected a2 =  300
C : public a1 =  200, protected a2 =  20, public b1 =  30
----------------------
A : public a1 =  10, protected a2 =  20
B : public a1 =  100, protected a2 =  300
C : public a1 =  200, protected a2 =  400, public b1 =  30
----------------------

分析：

1. 初始化：

   • 所有对象 (d, d1, d2) 的 a1 初始化为 10，a2 初始化为 20。d1 和 d2 中的 b1 初始化为 30。

     输出：

     A : public a1 =  10, protected a2 =  20
     B : public a1 =  10, protected a2 =  20
     C : public a1 =  10, protected a2 =  20, public b1 =  30
     ----------------------

2. 修改 d1.a1 为 100：

   • 只影响 d1 对象

     输出：

     A : public a1 =  10, protected a2 =  20
     B : public a1 =  100, protected a2 =  20
     C : public a1 =  10, protected a2 =  20, public b1 =  30
     ----------------------

3. 修改 d2.a1 为 200：

   • 只影响 d2 对象

     输出：

     A : public a1 =  10, protected a2 =  20
     B : public a1 =  100, protected a2 =  20
     C : public a1 =  200, protected a2 =  20, public b1 =  30
     ----------------------

4. 调用 d1.seta2(300)

   设置了 d1 对象中的 a2 值为 300。

   输出：

   A : public a1 =  10, protected a2 =  20
   B : public a1 =  100, protected a2 =  300
   C : public a1 =  200, protected a2 =  20, public b1 =  30
   ----------------------

5. 调用d2.seta2(400)

   设置了 d2 对象中的 a2 值为 400。

   输出：

   A : public a1 =  10, protected a2 =  20
   B : public a1 =  100, protected a2 =  300
   C : public a1 =  200, protected a2 =  400, public b1 =  30
   ----------------------

结论：

• 每个对象维护自己独立的成员变量（包括继承的变量）状态。
• 受保护的成员虽然在类及其子类之间可以访问和修改，但它们的状态是在每个对象级别上独立管理的。