1、继承访问权限测试：

1.1 继承的概念

面向对象程序设计中最重要的一个概念是继承。继承允许我们依据另一个类来定义一个类，这使得创建和维护一个应用程序变得更容易。这样做，也达到了重用代码功能和提高执行效率的效果。

当创建一个类时，您不需要重新编写新的数据成员和成员函数，只需指定新建的类继承了一个已有的类的成员即可。这个已有的类称为基类，新建的类称为派生类。

继承代表了 is a 关系。例如，哺乳动物是动物，狗是哺乳动物，因此，狗是动物，等等。

1.2 设计类A具有public, protected, private等不同属性的成员函数或变量

代码：

 class Person {public:string _name;protected:string _sex;private:int _age;};

这里新建了一个名为Person的类，public、protected和private分别带有一个变量。

1.3 类B通过public, protected, private等不同方式继承A，在类B的成员函数中测试访问A的成员函数或变量

代码：

class Pub_Student : public Person {  //public方式继承
public:void Test() {_name = "雷文晖";_sex = "男";}string _pubCn;
protected:string _pubSn;
private:int _pubGrade;
};
class pro_Student : protected Person {  //protected方式继承
public:void Test() {_name = "雷文晖";_sex = "男";}string proCn;
protected:string proSn;
private:int proGrade;
};class pri_Student : private Person {  //private方式继承
public:void Test() {_name = "雷文晖";_sex = "男";}string _priCn;
protected:string _priSn;
private:int _priGrade;
};

1.4 在类B中添加public, protected, private等不同属性的成员函数或变量，在外部测试访问B的各个成员函数或变量

 class Pub_Student : public Person {  //public方式继承
public:void Test() {_name = "雷文晖";_sex = "男";}string _pubCn;
protected:string _pubSn;
private:int _pubGrade;
};
class pro_Student : protected Person {  //protected方式继承
public:void Test() {_name = "雷文晖";_sex = "男";}string _proCn;
protected:string _proSn;
private:int _proGrade;
};class pri_Student : private Person {  //private方式继承
public:void Test() {_name = "雷文晖";_sex = "男";}string _priCn;
protected:string _priSn;
private:int _priGrade;
};

测试代码：

int main()
{Person a;cout<<a._name;//cout << a._age; _age为private 不可访问//cout << a._sex; _sex为protected 不可访问PubStudent b1;cout << b1._pubCn;b1.Test();cout << b1._name;//cout << b1._sex; _sex为protected 不可访问//cout << b1._age; _age为private 不可访问//cout << b1._pubSn; _pubSn为protected 不可访问//cout << b1._pubGrade; pubGrade为protected 不可访问ProStudent b2;cout << b2._proCn;b2.Test();//cout << b2._name; _name由public被降级为protected 不可访问//cout << b2._sex; _sex为protected 不可访问//cout << b2._age; _age为private 不可访问//cout << b2._proSn; _pubSn为protected 不可访问//cout << b2._proGrade; pubGrade为protected 不可访问PriStudent b3;cout << b3._priCn;b3.Test();//cout << b3._name; _name由public被降级为private 不可访问//cout << b3._sex; _sex由protected被降级为private 不可访问//cout << b3._age; _age为private 不可访问//cout << b3._priSn; _pubSn为protected 不可访问//cout << b3._priGrade; pubGrade为protected 不可访问
}

1.5 B以private方式继承A，尝试把A中的部分public成员提升为public

代码：

 class PriStudent : private Person {
public:void Test() {_name = "雷文晖";_sex = "男";}string _priCn;using Person::_name;
protected:string _priSn;
private:int _priGrade;
};

只需要添加一句“using Person::_name”便可以把继承过来的基类public变量升级为public
如果想让这些继承而来的数据成员作为public或者protected成员，可以用using重新声明
using声明语句中名字的访问权限由该using声明语句之前的访问说明符决定

2、友元类继承测试

概念

友元关系不能继承。基类的友元对派生类的成员没有特殊访问权限。
如果基类被授予友元关系，则只有基类具有特殊访问权限，该基类的派生类不能访问授予友元关系的类。
友元关系是单向的，不具有交换性。友元关系也不具有传递性。

2.1 设计类A含有私有变量a，在类A中友元给类C

class Person {
private:string _name;friend class Teacher;
};

这里有一个类Person，友元给类Teacher

2.2 设计类B继承A，添加私有变量b；在类C中测试访问类B的成员变量a, b

class Student : public Person {
private:int _grade;
};
class Teacher {
public:void Test() {Student b1;b1._name;//b1._grade;}
};

2.3 设计类D继承C，在D的成员函数中测试访问类A的成员变量a，类B的成员变量a, b

class Mr_W :public Teacher {
public:void Test() {Person a1;//a1._name; _name为private，不可访问Student a2; //a2._name; _name为private，不可访问//a2._grade; _grade为private，不可访问}
};

3、多态性综合运用

3.1 多态性的概念

在面向对象方法中，所谓多态性就是不同对象收到相同消息，产生不同的行为。在C++程序设计中，多态性是指用一个名字定义不同的函数，这些函数执行不同但又类似的操作，这样就可以用同一个函数名调用不同内容的函数。换言之，可以用同样的接口访问功能不同的函数，从而实现“一个接口，多种方法”。

事实上，在程序设计中经常会使用到多态性。最简单的例子就是运算符了，例如我们使用运算符+，就可以实现整型数、浮点数、双精度类型之间的加法运算，这三种类型的加法操作其实是互不相同的，是由不同内容的函数实现的。这个例子就是使用了多态的特征。

静态联编支持的多态性称为编译时多态性（静态多态性）。在C++中，编译时多态性是通过函数重载和模板实现的。利用函数重载机制，在调用同名函数时，编译系统会根据实参的具体情况确定索要调用的是哪个函数。

动态联编所支持的多态性称为运行时多态（动态多态）。在C++中，运行时多态性是通过虚函数来实现的。

3.2 多态性综合应用

前期准备： vs2019和xege
具体安装教程这里推荐看此博主的：
EGE的介绍、安装和使用

CShape.h

#ifndef CSHAPE_H
#define CSHAPE_H
#include<string>
#include<math.h>
using namespace std;class CPoint;
class CRect;
class CShape
{
public:CShape();CShape(const CShape& shape);virtual ~CShape();virtual double GetArea() const;virtual bool ptIn(const CPoint& pt) const;virtual bool InRect(const CRect& rc) const;virtual void Draw() const;virtual void DrawColor();virtual CShape* Clone() const;virtual CShape& Move(int nOffsetX, int nOffsetY);protected:string m_sName;
};class CPoint :public CShape {
public:int m_nPosX;int m_nPosY;CPoint() {m_nPosX = 0;m_nPosY = 0;}CPoint(int nPosX, int nPosY);CPoint(const CPoint& pt);virtual ~CPoint();double GetArea() const;bool ptIn(const CPoint& pt) const;bool InRect(const CRect& rc) const;void Draw() const;void DrawColor();CPoint* Clone() const;CPoint& Move(int nOffsetX, int nOffsetY);
};
class CTriangle :virtual public CShape {
public:CTriangle() {}CTriangle(const CPoint& pt1, const CPoint& pt2, const CPoint& pt3);CTriangle(const CTriangle& rc);CTriangle(const CPoint& pt);virtual ~CTriangle();double GetArea() const;bool ptIn(const CPoint& pt) const;bool InRect(const CRect& rc) const;void Draw() const;void DrawColor();CShape* Clone() const;CShape& Move(int nOffsetX, int nOffsetY);CPoint m_pts[3];
};class CRect :virtual public CShape {
public:CRect() {}CRect(CPoint pt1, CPoint pt2);CRect(const CRect& rc);CRect(CPoint pt1);virtual ~CRect();double GetArea() const;bool ptIn(const CPoint& pt) const;bool InRect(const CRect& rc) const;void Draw() const;void DrawColor();CShape* Clone() const;CShape& Move(int nOffsetX, int nOffsetY);CPoint m_ptLT;CPoint m_ptBR;
};class Comgraphics :public CRect, public CTriangle {
public:Comgraphics(const CRect& pt1);Comgraphics(const Comgraphics& rc);Comgraphics(const CPoint pt1);virtual ~Comgraphics();double GetArea() const;bool ptIn(const CPoint& pt) const;bool InRect(const CRect& rc) const;void Draw() const;void DrawColor();CShape* Clone() const;CShape& Move(int nOffsetX, int nOffsetY);CPoint m_pt1;CPoint m_pt2;};
#endif

CShape.cpp

#include "CShape.h"
#include "graphics.h"
#include <iostream>
using namespace std;
//CShape
CShape::CShape()
{
}
CShape::CShape(const CShape& shape) {m_sName = shape.m_sName;
}
CShape::~CShape()
{
}
double CShape::GetArea() const {return 0;
}
bool CShape::ptIn(const CPoint& pt) const {return false;
}
bool CShape::InRect(const CRect& rc) const {return false;
}
void CShape::Draw() const
{
}
void CShape::DrawColor()
{
}
CShape* CShape::Clone() const {return new CShape(*this);
}
CShape& CShape::Move(int nOffsetX, int nOffsetY) {return *this;
}//CPoint
CPoint::CPoint(int nPosX, int nPosY) {m_nPosX = nPosX;m_nPosY = nPosY;
}
CPoint::CPoint(const CPoint& pt) {m_nPosX = pt.m_nPosX;m_nPosY = pt.m_nPosY;
}
CPoint::~CPoint() {//cout << "CPoint::~CPoint()\n";
}
double CPoint::GetArea() const {return 0;
}
bool CPoint::ptIn(const CPoint& pt) const {return false;
}
bool CPoint::InRect(const CRect& rc) const {return rc.ptIn(*this);
}
void CPoint::Draw() const {circle(m_nPosX, m_nPosY, 2);
}
void CPoint::DrawColor()
{
}
CPoint* CPoint::Clone() const {return new CPoint(*this);
}
CPoint& CPoint::Move(int nOffsetX, int nOffsetY) {m_nPosX += nOffsetX;m_nPosY += nOffsetY;return *this;
}//CTriangle
CTriangle::CTriangle(const CTriangle& tri) {for (int i = 0; i < 3; i++) {m_pts[i] = tri.m_pts[i];}
}
CTriangle::~CTriangle() {//cout << "CTriangle::~CTriangle()\n";
}
CTriangle::CTriangle(const CPoint& pt1, const CPoint& pt2, const CPoint& pt3) {m_pts[0] = pt1;m_pts[1] = pt2;m_pts[2] = pt3;
}
CTriangle::CTriangle(const CPoint& pt)
{CPoint* pt1 = new CPoint(pt.m_nPosX + 100, pt.m_nPosY + 90);CPoint* pt2 = new CPoint(pt.m_nPosX, pt.m_nPosY + 90);m_pts[0] = pt;m_pts[1] = *pt1;m_pts[2] = *pt2;
}CShape& CTriangle::Move(int nOffsetX, int nOffsetY) {for (int i = 0; i < 3; i++) {m_pts[i].Move(nOffsetX, nOffsetY);}return *this;
}
double CTriangle::GetArea() const {int x1, y1, x2, y2, x3, y3;x1 = m_pts[0].m_nPosX;y1 = m_pts[0].m_nPosY;x2 = m_pts[1].m_nPosX;y2 = m_pts[1].m_nPosY;x3 = m_pts[2].m_nPosX;y3 = m_pts[2].m_nPosY;double bottomLine = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));double verticalLine1 = abs((y1 - y2) * x3 - (x1 - x2) * y3 + (x1 - x2) * y2 - (y1 - y2) * x2);double verticalLine2 = sqrt(pow(y1 - y2, 2) + pow(x1 - x2, 2));double verticalLine = verticalLine1 / verticalLine2;return (verticalLine * bottomLine) / 2.0;
}
bool CTriangle::ptIn(const CPoint& pt) const {CTriangle c1 = CTriangle(m_pts[0], m_pts[1], pt);CTriangle c2 = CTriangle(m_pts[1], m_pts[2], pt);CTriangle c3 = CTriangle(m_pts[2], m_pts[0], pt);double totalArea = c1.GetArea() + c2.GetArea() + c3.GetArea();if (totalArea == this->GetArea())return true;elsereturn false;
}
bool CTriangle::InRect(const CRect& rc) const {return rc.ptIn(m_pts[0]) && rc.ptIn(m_pts[1]) && rc.ptIn(m_pts[2]);
}
void CTriangle::Draw() const {int poly[8] = { m_pts[0].m_nPosX ,m_pts[0].m_nPosY,m_pts[1].m_nPosX,m_pts[1].m_nPosY,m_pts[2].m_nPosX,m_pts[2].m_nPosY, m_pts[0].m_nPosX ,m_pts[0].m_nPosY };setfillcolor(EGERGB(0xFF, 0xFF, 0xFF));fillpoly(4, poly);
}
void CTriangle::DrawColor() {int poly[8] = { m_pts[0].m_nPosX ,m_pts[0].m_nPosY,m_pts[1].m_nPosX,m_pts[1].m_nPosY,m_pts[2].m_nPosX,m_pts[2].m_nPosY, m_pts[0].m_nPosX ,m_pts[0].m_nPosY };setfillcolor(EGERGB(0xFF, 0xA5, 0x00));fillpoly(4, poly);
}
CShape* CTriangle::Clone() const {return new CTriangle(*this);
}//CRect
CRect::CRect(CPoint pt1, CPoint pt2) {m_ptLT = CPoint(min(pt1.m_nPosX, pt2.m_nPosX), min(pt1.m_nPosY, pt2.m_nPosY));m_ptBR = CPoint(max(pt1.m_nPosX, pt2.m_nPosX), max(pt1.m_nPosY, pt2.m_nPosY));
}
CRect::CRect(const CRect& rc) {m_ptLT = rc.m_ptLT;m_ptBR = rc.m_ptBR;
}
CRect::CRect(CPoint pt1)
{m_ptLT = CPoint(pt1.m_nPosX, pt1.m_nPosY);m_ptBR = CPoint(pt1.m_nPosX + 100, pt1.m_nPosY + 100);
}
CRect::~CRect() {// cout << "CRect::CRect()\n";
}
double CRect::GetArea() const {return (m_ptBR.m_nPosX - m_ptLT.m_nPosX) * (m_ptBR.m_nPosY - m_ptLT.m_nPosY);
}
bool CRect::ptIn(const CPoint& pt) const {return (pt.m_nPosX >= m_ptLT.m_nPosX && pt.m_nPosX <= m_ptBR.m_nPosX) &&(pt.m_nPosY >= m_ptLT.m_nPosY && pt.m_nPosY <= m_ptBR.m_nPosY);
}
bool CRect::InRect(const CRect& rc) const {return rc.ptIn(m_ptLT) && rc.ptIn(m_ptBR);
}
void CRect::Draw() const {// 存储n个顶点的x,y坐标int pts[10] = { m_ptLT.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptLT.m_nPosY };// 绘制n个顶点的多边形，第一个参数必须要传入n+1，pts最后一个顶点坐标和第一个相同//drawpoly(5, pts);setfillcolor(EGERGB(0xFF, 0xFF, 0xFF));fillpoly(5, pts);
}
void CRect::DrawColor() {int pts[10] = { m_ptLT.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptLT.m_nPosY };// 绘制n个顶点的多边形，第一个参数必须要传入n+1，pts最后一个顶点坐标和第一个相同setfillcolor(EGERGB(0xFF, 0xA5, 0x00));fillpoly(5, pts);
}
CShape* CRect::Clone() const {return new CRect(*this);
}
CShape& CRect::Move(int nOffsetX, int nOffsetY) {m_ptLT.Move(nOffsetX, nOffsetY);m_ptBR.Move(nOffsetX, nOffsetY);return *this;}
//Comgraphics
Comgraphics::Comgraphics(const CRect& pt1) {m_pt1.m_nPosX = pt1.m_ptBR.m_nPosX;m_pt1.m_nPosY = pt1.m_ptLT.m_nPosY + (pt1.m_ptBR.m_nPosY - pt1.m_ptLT.m_nPosY) / 2;m_pt2.m_nPosX = pt1.m_ptLT.m_nPosX + (pt1.m_ptBR.m_nPosX - pt1.m_ptLT.m_nPosX) / 2;m_pt2.m_nPosY = pt1.m_ptBR.m_nPosY;m_ptLT = pt1.m_ptLT;m_ptBR = pt1.m_ptBR;}
Comgraphics::Comgraphics(const Comgraphics& rc) {m_pt1 = rc.m_pt1;m_pt2 = rc.m_pt2;m_ptBR = rc.m_ptBR;m_ptLT = rc.m_ptLT;
}
Comgraphics::Comgraphics(const CPoint pt1) {m_ptLT = CPoint(pt1.m_nPosX, pt1.m_nPosY);m_ptBR = CPoint(pt1.m_nPosX + 60, pt1.m_nPosY + 80);
}
Comgraphics::~Comgraphics() {cout << "Comgraphics::~Comgraphics()" << endl;}
double Comgraphics::GetArea()  const {return 0.0;
}
bool Comgraphics::ptIn(const CPoint& pt) const {return (pt.m_nPosX >= m_ptLT.m_nPosX && pt.m_nPosX <= m_ptBR.m_nPosX) &&(pt.m_nPosY >= m_ptLT.m_nPosY && pt.m_nPosY <= m_ptBR.m_nPosY);
}
bool Comgraphics::InRect(const CRect& rc) const const {return rc.ptIn(m_ptLT) && rc.ptIn(m_ptBR);
}
void Comgraphics::Draw() const {// 存储n个顶点的x,y坐标int pts[10] = { m_ptLT.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptLT.m_nPosY };// 绘制n个顶点的多边形，第一个参数必须要传入n+1，pts最后一个顶点坐标和第一个相同//drawpoly(5, pts);setfillcolor(GREEN);fillpoly(5, pts);line(m_pt1.m_nPosX, m_pt1.m_nPosY, m_pt2.m_nPosX, m_pt2.m_nPosY);line(m_ptLT.m_nPosX, m_ptLT.m_nPosY, m_pt2.m_nPosX, m_pt2.m_nPosY);line(m_pt1.m_nPosX, m_pt1.m_nPosY, m_ptLT.m_nPosX, m_ptLT.m_nPosY);
}
void Comgraphics::DrawColor() {// 存储n个顶点的x,y坐标int pts[10] = { m_ptLT.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptLT.m_nPosY,m_ptBR.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptBR.m_nPosY,m_ptLT.m_nPosX,m_ptLT.m_nPosY };// 绘制n个顶点的多边形，第一个参数必须要传入n+1，pts最后一个顶点坐标和第一个相同setfillcolor(YELLOW);fillpoly(5, pts);line(m_pt1.m_nPosX, m_pt1.m_nPosY, m_pt2.m_nPosX, m_pt2.m_nPosY);line(m_ptLT.m_nPosX, m_ptLT.m_nPosY, m_pt2.m_nPosX, m_pt2.m_nPosY);line(m_pt1.m_nPosX, m_pt1.m_nPosY, m_ptLT.m_nPosX, m_ptLT.m_nPosY);
}
CShape* Comgraphics::Clone() const {return new Comgraphics(*(this));
}CShape& Comgraphics::Move(int nOffsetX, int nOffsetY) {m_ptLT.Move(nOffsetX, nOffsetY);m_ptBR.Move(nOffsetX, nOffsetY);m_pt1.Move(nOffsetX, nOffsetY);m_pt2.Move(nOffsetX, nOffsetY);return *this;
}

Main.cpp

#include<vector>
#include "graphics.h"
#include<iostream>
#include "CShape.h"
using namespace std;int main()
{//图形画布基础设置initgraph(640, 480);setbkcolor(WHITE);delay_ms(0);setcolor(BLACK);setfont(20, 0, "楷体");setbkmode(TRANSPARENT);//enter+左击-->新建矩形");//enter+右击-->新建三角形");//enter+滚轮中间-->新建组合图形//ctrl+左击-->复制图形");//ctrl+右击-->粘贴图形");vector<CShape*>shapes;vector<CShape*>shapestmp;shapes.push_back(new CTriangle(CPoint(320, 320), CPoint(250, 340), CPoint(340, 450)));//shapes.push_back(new CTriangle(CPoint(10, 10), CPoint(150, 10), CPoint(150, 150)));shapes.push_back(new CRect(CPoint(200, 200), CPoint(300, 300)));shapes.push_back(new Comgraphics(CRect(CPoint(250, 50))));//移动bool move_flag = false;bool copy_flag = false;bool redraw = true;//鼠标点击时记录它的坐标int clickX, clickY;int copyX, copyY;int checkedid = -1;int copyid = -1;for (; is_run(); delay_fps(60)) {while (mousemsg()) {mouse_msg msg = getmouse();//判断鼠标的移动if (msg.is_move()) {if (checkedid != -1) {if (move_flag) {shapes[checkedid]->Move(msg.x - clickX, msg.y - clickY);}}clickX = msg.x;clickY = msg.y;redraw = true;}// 判断鼠标左键else if (msg.is_left()) {// 判断鼠标左键是否按下if (msg.is_down()) {clickX = msg.x;clickY = msg.y;CPoint pt = CPoint(clickX, clickY);int isIn = 0;for (int i = 0; i < shapes.size(); i++) {if (shapes[i]->ptIn(pt)) {isIn = 1;//如果鼠标在图形区域内就设置移动的flag为truemove_flag = true;checkedid = i;redraw = true;break;}}if (isIn == 0)checkedid = -1;}else {move_flag = false;}}}// 重新绘图if (redraw) {redraw = false;cleardevice();for (int i = 0; i < shapes.size(); i++) {if (i == checkedid)shapes[i]->DrawColor();elseshapes[i]->Draw();}}while (kbmsg()) {key_msg msgk = getkey();if (msgk.key == key_enter && msgk.msg == key_msg_down) {mouse_msg msgm = getmouse();if (msgm.is_left()) {// 判断鼠标左键是否按下if (msgm.is_down()) {shapes.push_back(new CRect(CPoint(msgm.x, msgm.y)));redraw = true;}}if (msgm.is_right()) {// 判断鼠标右键是否按下if (msgm.is_down()) {shapes.push_back(new CTriangle(CPoint(msgm.x, msgm.y)));redraw = true;}}if (msgm.is_mid()) {CRect r1 = CRect(CPoint(msgm.x, msgm.y));// 判断鼠标中键是否按下if (msgm.is_down()) {shapes.push_back(new Comgraphics(r1));redraw = true;}}}if (msgk.key == key_control && msgk.msg == key_msg_down) {mouse_msg msgm = getmouse();if (msgm.is_left()) {// 判断鼠标左键是否按下if (msgm.is_down()) {copyX = msgm.x;copyY = msgm.y;CPoint pt = CPoint(copyX, copyY);for (int i = 0; i < shapes.size(); i++) {if (shapes[i]->ptIn(pt)) {//如果鼠标在图形区域内就设置移动的flag为truecopy_flag = true;copyid = i;break;}}}}if (msgm.is_right()) {// 判断鼠标右键是否按下if (msgm.is_down()) {if (copy_flag == true) {shapes.push_back(&(shapes[copyid]->Clone())->Move(msgm.x - copyX, msgm.y - copyY));redraw = true;}}}}}}closegraph();return 0;
}

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