T1:

 

 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 }

 微调后（加virtual）

 

1.对于同名的函数，继承类会将基类的函数覆盖掉。
2.对于继承的类的对象，可以通过 对象.基类::(同名)函数 的方式来访问被覆盖掉的同名函数。
3.公有派生类对象可以替代基类对象的位置。
4.添加了virtual后，fun函数输出不同。通过使函数变为虚拟函数，可以使派生类对象指针模拟为基类对象来使调用函数发生改变。

 

 

 

 

T2:

Car.hpp

 1 #include<iostream>
 2 #include<string>
 3 using namespace std;
 4 class Car {
 5 public:
 6     Car(string mk,string md,double y,double dm = 0):maker(mk),model(md),year(y),odometers(0){}
 7     void info();
 8     void update_odometers(const double u_om);
 9 private:
10     string maker, model;
11     double year, odometers = 0;
12 };
13 void Car::info() {
14     cout << "Manufacturer:\t\t" << maker << endl;
15     cout << "Model:\t\t\t" << model << endl;
16     cout << "Manuf.Year:\t\t" << year << endl;
17     cout << "Current odometers:\t" << odometers << endl;
18 
19 }
20 void Car::update_odometers(const double u_om) {
21     if (u_om <= odometers) {
22         cout << "WARNING!The updated data is under current odometers!" << endl;
23         return;
24     }
25     else
26         odometers = u_om;
27 }

Battery.hpp

 1 #include<iostream>
 2 using namespace std;
 3 class Battery {
 4 public:
 5     Battery(double cp=70):capacity(cp){}
 6     double get_capacity() { return capacity; }
 7 
 8 private:
 9     double capacity;
10 };

electricCar.hpp

 1 #include<iostream>
 2 #include<string>
 3 #include"Battery.hpp"
 4 #include"Car.hpp"
 5 using namespace std;
 6 class ElectricCar :public Car {
 7 public:
 8     ElectricCar(string mk, string md, double y, double dm=0, double btr=70) :Car(mk,md,y,dm), battery(btr){}
 9     void info();
10 private:
11     Battery battery;
12 };
13 void ElectricCar::info() {
14     Car::info();
15     cout << "Current Capacity:\t" << battery.get_capacity() << " kWh " << endl;
16 
17 }

task.cpp

 1 #include <iostream>
 2 #include "electricCar.hpp"
 3 
 4 int main()
 5 {
 6     using namespace std;
 7 
 8     // test class of Car
 9     Car oldcar("Audi", "a4", 2016);
10     cout << "--------oldcar's info--------" << endl;
11     oldcar.update_odometers(18000);
12     oldcar.info();
13 
14     cout << endl;
15 
16     // test class of ElectricCar
17     ElectricCar newcar("Tesla", "model s", 2016);
18     newcar.update_odometers(2800);
19     cout << "\n--------newcar's info--------\n";
20     newcar.info();
21     
22     //test update_odometers error
23     cout << "\n--------error test--------\n";
24     oldcar.update_odometers(10000);
25     oldcar.info();
26 }

 

T3:

pets.hpp

 1 #include<iostream>
 2 #include<string>
 3 using namespace std;
 4 
 5 class MachinePets {
 6 public:
 7     MachinePets(const string s):nickname(s){}
 8     string get_nickname() const { return nickname; }
 9     virtual string talk() { return " "; }
10 private:
11     string nickname;
12 };
13 
14 class PetCats :public MachinePets {
15 public:
16     PetCats(const string s):MachinePets(s){}
17     string talk() { return "Meow ~ Meow ~ ~\n"; }
18 };
19 
20 class PetDogs :public MachinePets {
21 public:
22     PetDogs(const string s):MachinePets(s){}
23     string talk() { return "Woof! Woof!!\n"; }
24 };

task.cpp

 1 #include <iostream>
 2 #include "pets.hpp"
 3 
 4 void play(MachinePets *ptr)
 5 {
 6     std::cout << ptr->get_nickname() << " says " << ptr->talk() << std::endl;
 7 }
 8 
 9 int main()
10 {
11     PetCats cat("Garfield");
12     PetDogs dog("Snoopy");
13 
14     play(&cat);
15     play(&dog);
16 }