实验4 继承
- 实验任务二
source code ：
1 #include <iostream> 2 #include <typeinfo> 3 4 // definitation of Graph 5 class Graph 6 { 7 public: 8 void draw() { std::cout << "Graph::draw() : just as an interface\n"; } 9 }; 10 11 12 // definition of Rectangle, derived from Graph 13 class Rectangle : public Graph 14 { 15 public: 16 void draw() { std::cout << "Rectangle::draw(): programs of draw a rectangle\n"; } 17 }; 18 19 20 // definition of Circle, derived from Graph 21 class Circle : public Graph 22 { 23 public: 24 void draw() { std::cout << "Circle::draw(): programs of draw a circle\n"; } 25 }; 26 27 28 // definitaion of fun(): as a call interface 29 void fun(Graph *ptr) 30 { 31 std::cout << "pointer type: " << typeid(ptr).name() << "\n"; 32 std::cout << "RTTI type: " << typeid(*ptr).name() << "\n"; 33 ptr -> draw(); 34 } 35 36 // test 37 int main() 38 { 39 Graph g1; 40 Rectangle r1; 41 Circle c1; 42 43 // call by object name 44 g1.draw(); 45 r1.draw(); 46 c1.draw(); 47 48 std::cout << "\n"; 49 50 // call by object name, and using the scope resolution operator:: 51 r1.Graph::draw(); 52 c1.Graph::draw(); 53 54 std::cout << "\n"; 55 56 // call by pointer to Base class 57 fun(&g1); 58 fun(&r1); 59 fun(&c1); 60 }
The Running results ：
对代码稍作改动，在基类Graph的成员函数draw()前面加一个关键字virtual，重新编译运行程序，再次观察结果，对比一下
如果派生类中声明了与基类成员函数同名的新函数,即使函数的参数表不同,从基类继承的同名函数的所有重载形式也都会被隐藏。
- 实验任务三
source code ：
1 #include"battery.hpp" 2 #include"car.hpp" 3 #include<iomanip> 4 5 class ElectricCar:public Car{ 6 public: 7 ElectricCar(string s1,string s2,int a,int b=0,int ca=70):Car(s1,s2,a,b),battery(ca){}; 8 void info() const { 9 Car::info(); 10 cout<<left<<setw(20)<<"capacity: "<<battery.get_capacity()<<"-kWh"<<endl; 11 } 12 private: 13 Battery battery; 14 };
1 #include<iostream> 2 #include<string> 3 4 using namespace std; 5 6 class Battery{ 7 public: 8 Battery(int b=70):capacity(b){}; //Battery 9 int get_capacity() const{return capacity;} 10 private: 11 int capacity; 12 };
1 #include<iostream> 2 #include<string> 3 4 #include<iomanip> 5 6 using namespace std; 7 8 class Car{ 9 10 public: 11 Car(string s1,string s2,int a,int b=0):maker(s1),model(s2),year(a),odometers(b){}; 12 void info() const { 13 cout<<left<<setw(20)<<"maker: "<<maker<<endl; 14 cout<<left<<setw(20)<<"model: "<<model<<endl; 15 cout<<left<<setw(20)<<"year: "<<year<<endl; 16 cout<<left<<setw(20)<<"odometers: "<<odometers<<endl; 17 } 18 void update_odometers(int meters){ 19 if(meters<odometers){ 20 cout<<"incorrect number! "<<endl; 21 } 22 23 else{ 24 odometers=meters; 25 } 26 27 } 28 private: 29 string maker; 30 string model; 31 int year, odometers; 32 };
The Running results ：
- 实验任务4
source code ：
1 #include <iostream> 2 using namespace std; 3 4 class MachinePets{ 5 public: 6 MachinePets(const string s):nickname(s){ 7 }; 8 string get_nickname() const{return nickname;}; 9 virtual string talk(){ 10 }; 11 ~MachinePets(){ 12 }; 13 14 private: 15 string nickname; 16 }; 17 class PetCats:public MachinePets{ 18 public: 19 PetCats(const string s):MachinePets(s){ 20 21 }; 22 23 string talk(){ 24 return "miao wu~"; 25 } 26 }; 27 class PetDogs:public MachinePets{ 28 public: 29 30 PetDogs(const string s):MachinePets(s){ 31 32 }; 33 string talk(){ 34 return "wang wang~"; 35 } 36 };
The Running results ：
