权限对继承的影响
当使用protected继承时，所使用的基类成员时为public会换成protected 再去看下面的protected权限 类内部是可以访问的 但是同一类的对象是不能访问的 同理
cpp
#include <iostream>
using namespace std;
//基类，父类
class Vehicle{//交通工具，车，抽象的概念
public:
string type;
string contry;
string color;
double price;
int numOfWheel;
protected:
int protectedData;
private:
int privateData;
public:
void run();
void stop();
};
//派生类, 子类
class Roadster : protected Vehicle { //跑车，也是抽象，比父类感觉上范围缩小点 子类：public 父类 （因为或默认private）
public:
void openTopped(){
type="wefrwr"; //在这里type是protected
}
void pdrifting();
};
int main()
{
Roadster ftype;
ftype.type ="捷豹Ftype"; //这里type是protected 不能在同一类对象中访问
return 0;
}基类/派生类构造函数
Roadster(string contry,double price,int state) :Vehicle(contry,price)
cpp
#include <iostream>
using namespace std;
//基类，父类
class Vehicle{ //交通工具，车，抽象的概念
public:
string contry;
double price;
Vehicle(string contry,double price){
cout << "基类的构造函数被调用" << endl;
this->contry =contry;
this->price = price;
}
};
//派生类，子类
class Roadster : public Vehicle{
public:
int stateOfTop;
Roadster(string contry,double price,int state) :Vehicle(contry,price){
cout << "派生类的构造函数被调用" << endl;
stateOfTop =state;
}
};
int main()
{
Roadster FTYPE("法国",70,0);
return 0;
}虚函数
在C++中，virtual和override 关键字用于支持多态，尤其是在涉及继承和方法重写下的情况下
Virtual关键字
使用场景：在基类中声明虚函数
virtual void func（）
目的：允许派生类重写该函数，实现多态，
cpp
class Vehicle{ //交通工具，车，抽象的概念
public:
string contry;
double price;
Vehicle(){};
Vehicle(string contry,double price){
cout << "基类的构造函数被调用" << endl;
this->contry =contry;
this->price = price;
};
//基类中声明了一个虚函数
virtual void run(){
cout << "车跑起来了" << endl;
}
};override关键字
使用场景:在基类中重写虚函数
目的：明确指示函数意图重写基类的虚函数
cpp
class Bike : public Vehicle{
public:
void run() override{
cout << "脚踩自行车" << endl ;
}
};
cpp
#include <iostream>
using namespace std;
//基类，父类
class Vehicle{ //交通工具，车，抽象的概念
public:
string contry;
double price;
Vehicle(){};
Vehicle(string contry,double price){
cout << "基类的构造函数被调用" << endl;
this->contry =contry;
this->price = price;
};
//基类中声明了一个虚函数
virtual void run(){
cout << "车跑起来了" << endl;
}
};
//派生类，子类
class Bike : public Vehicle{
public:
void run() override{
cout << "脚踩自行车" << endl ;
}
};
int main()
{
Bike b;
b.run();
return 0;
}override仅应用于派生类中重写基类的虚函数
如果类中有虚函数，通常应该将析构函数也声明为虚的
一旦在基类中声明为虚函数，该函数在所有派生类中自动成为虚函数，无论是否使用virtual关键字
多重继承
cpp
#include <iostream>
using namespace std;
class classA{
public:
void displayA(){
cout << "Displaying ClassA" << endl;
}
void testFunc(){
cout << "testFunc ClassA" <<endl;
}
};
class classB{
public:
void displayB(){
cout << "Displaying classB" << endl;
}
void testFunc(){
cout << "testFunc ClassB" <<endl;
}
};
class Derived : public classA,public classB{
public:
void display(){
displayA();
displayB();
classA::testFunc(); //如果在两个类中有相同的函数 那么应该表明是哪一个类
}
};
int main()
{
Derived obj;
obj.displayA();
obj.displayB();
obj.display();
return 0;
}菱形继承
中间的必须采用虚拟继承才可以
class Derived1: virtual public Baseclass Derived2: virtual public Base
cpp
#include <iostream>
using namespace std;
class Base{
public:
int data;
Base(int data){
this->data=data;
}
void pritInfo(){
cout << data << endl;
}
};
class Derived1: virtual public Base {
//继承自 Base
public:
Derived1(int data) : Base(data){
}
};
class Derived2: virtual public Base {
//继承自 Base
public:
Derived2(int data) : Base(data){
}
};
class FinalDerived : public Derived1,public Derived2{
//继承自 Derived1 和 Derived2
public:
FinalDerived(int data) : Base(data),Derived1(data),Derived2(data){
}
};
int main()
{
FinalDerived final(10);
final.pritInfo();
return 0;
}注意：
FinalDerived(int data) : Base(data),Derived1(data),Derived2(data)多态
RemoteCon *remoteCon =new TvRemoCon; //多态 向下兼容
remoteCon->openUtils();
cpp
#include <iostream>
using namespace std;
class RemoteCon{
public:
virtual void openUtils(){
cout <<"遥控器的开被按下" << endl;
};
};
class TvRemoCon : public RemoteCon{
public:
void openUtils() override{
cout << "电视遥控器的开被按下" << endl;
}
};
class RoundspeakerCon : public RemoteCon{
public:
void openUtils() override{
cout << "音响遥控器的开被按下" << endl;
}
};
class lightCon: public RemoteCon{
public:
void openUtils() override{
cout << "灯光遥控器的开被按下" << endl;
}
};
void test(RemoteCon& r)
{
r.openUtils();
}
int main()
{
RemoteCon *remoteCon =new TvRemoCon; //多态 向下兼容
remoteCon->openUtils();
RemoteCon *remoteCon2 =new RoundspeakerCon; //多态
remoteCon2->openUtils();
RemoteCon *remoteCon3 =new lightCon; //多态
remoteCon3->openUtils();
TvRemoCon tvRemote;
test(tvRemote);
return 0;
}结果：
抽象类：
抽象类，不支持被实例化 即派生类不把所有的基类中函数重新定义 那么就会报错
抽象类 也是支持多态的
cpp
#include <iostream>
using namespace std;
class Teacher{
public:
string name;
string school;
string major;
virtual void goInClass()=0;
virtual void startTeaching() =0;
virtual void afterTeaching() =0;
};
class EnglishTeacher : public Teacher{
public:
void goInClass() override{
cout << "英语老师开始进入教室" << endl;
}
void startTeaching() override{
cout << "英语老师开始教学" << endl ;
}
void afterTeaching() override{
}
};
int main()
{
//Teacher t; //抽象类，不支持被实例化 即派生类不把所有的基类中函数重新定义 那么就会报错
EnglishTeacher e;
e.goInClass();
//抽象类 也是支持多态的
Teacher *s = new EnglishTeacher();
s->startTeaching();
return 0;
}