註意派生類構造函數的寫法。

  1 #include <iostream>
  2 
  3 using namespace std;
  4 
  5 enum COLOR { Red, Green, Blue, Yellow, White, Black, Brown };
  6 
  7 class Animal
  8 {
  9 public:
 10     Animal() = default;
 11     Animal(int);
 12     virtual ~Animal();
 13     virtual int GetAge() const { return
 
 itsAge; }
 14     virtual void SetAge(int age) { itsAge = age; }
 15     virtual void Sleep() const = 0;                //抽象基類，有5個純虛函數
 16     virtual void Eat() const = 0;
 17     virtual void Reproduce() const = 0;  //繁殖
 18     virtual void Move() const = 0;
 19     virtual void Speak() const = 0;
 20 private
 
:
 21     int itsAge;
 22 };
 23 
 24 Animal::Animal(int age): itsAge(age)
 25 {
 26     cout << "Animal構造函數被調用...\n";
 27 }
 28 Animal::~Animal()
 29 {
 30     cout << "Animal析構函數被調用...\n";
 31 }
 32 
 33 class Mammal : public Animal
 34 {
 35 public:
 36     Mammal() = default;
 37     Mammal(int
 
 age) : Animal(age)   //將age傳遞給基類Animal的構造函數,使用基類的構造函數構造派生類的基類部分的成員
 38     {
 39         cout << "Mammal構造函數被調用...\n";
 40     }
 41     virtual ~Mammal()
 42     {
 43         cout << "Mammal析構函數被調用...\n";
 44     }
 45     virtual void Reproduce() const      //只覆蓋了基類Animal的Reproduce函數,基類的其他4個純虛函數沒有重寫，所以Mammal類還是一個抽象類(一個具有4個純虛函數的抽象類)
 46     {
 47         cout << "Mammal reproduction depicted...\n";
 48     }
 49 };
 50 
 51 class Fish : public Animal
 52 {
 53 public:
 54     Fish() = default;
 55     Fish(int age) : Animal(age)     //將age傳遞給基類Animal的構造函數,使用基類的構造函數構造派生類的基類部分的成員
 56     {
 57         cout << "Fish構造函數被調用...\n";
 58     }
 59     virtual ~Fish()
 60     {
 61         cout << "Fish的析構函數被調用...\n";
 62     }
 63     virtual void Sleep() const { cout << "Fish sleeping...\n"; }     //Fish類實現了Animal類的所有純虛函數，所以Fish類不是抽象類
 64     virtual void Eat() const { cout << "fish eating...\n"; }
 65     virtual void Reproduce() const { cout << "fish reproducing...\n"; }
 66     virtual void Move() const { cout << "Fish moving...\n"; }
 67     virtual void Speak() const { cout << "Fish speaking...\n"; };
 68 };
 69 
 70 class Horse : public Mammal
 71 {
 72 public:
 73     Horse() = default;
 74     Horse(int age, COLOR color) : Mammal(age), itsColor(color)
 75     {
 76         cout << "Horse構造函數被調用...\n";
 77     }
 78     virtual ~Horse()
 79     {
 80         cout << "Horse析構函數被調用...\n";
 81     }
 82     virtual void Speak() const { cout << "Horse speaking\n"; }//由於Horse繼承於Mammal,Mammal已經實現了Animal的Reproduce純虛函數，所以horse只需實現剩余4個純虛函數即可
 83     virtual void Sleep() const { cout << "Horse sleeping...\n"; }
 84     virtual void Eat() const { cout << "Horse eating"; }
 85     virtual void Move() const { cout << "Horse Moving...\n"; }
 86     virtual COLOR GetItsColor() const { return itsColor; }    //在繼承關系中，最好將所有成員函數都聲明為虛函數
 87 protected:
 88     COLOR itsColor;   //COLOR為前面定義的枚舉類型
 89 };
 90 
 91 class Dog : public Mammal
 92 {
 93 public:
 94     Dog() = default;
 95     Dog(int age, COLOR color) : Mammal(age), itsColor(color)
 96     {
 97         cout << "Dog構造函數被調用...\n";
 98     }
 99     virtual ~Dog()
100     {
101         cout << "Dog析構函數被調用...\n";
102     }
103     virtual void Sleep() const { cout << "Dog sleeping...\n"; }     
104     virtual void Eat() const { cout << "Dog eating...\n"; }
105     virtual void Reproduce() const { cout << "Dog reproducing...\n"; }  //覆蓋了父類Mammal的reproduce函數
106     virtual void Move() const { cout << "Dog moving...\n"; }
107     virtual void Speak() const { cout << "Dog speaking...\n"; }
108 protected:
109     COLOR itsColor;
110 };
111 
112 int main()
113 {
114     Animal *pAnimal = nullptr;
115     int choice;
116     bool fQuit = false;
117     while (fQuit == false)
118     {
119         cout << "(1)Dog (2)Horse (3)Fish (0)Quit: ";
120         cin >> choice;
121         
122         switch (choice)         //pAnimal可以指向其任意的子類對象
123         {                       //此處體現了類的多態性
124         case 1:                
125             pAnimal = new Dog(5, Brown);
126             break;
127         case 2:
128             pAnimal = new Horse(4, Black);
129             break;
130         case 3:
131             pAnimal = new Fish(5);
132             break;
133         default:
134             fQuit = true;
135             break;
136         }
137         if (fQuit == false)
138         {
139             pAnimal->Speak();
140             pAnimal->Eat();
141             pAnimal->Reproduce();
142             pAnimal->Move();
143             pAnimal->Sleep();
144             delete pAnimal;
145             cout << endl;
146         }
147     }
148 
149     return 0;
150 }

C++——類的綜合案例——純虛函數與抽象類( 加強對接口與多態，以及派生類構造函數的理解 )