C++学习之构造函数和析构函数

 1 /*
 2 
 3 
 4   实验启示1：构造子类对象时，先调用父类构造函数，后调用子类构造函数
 5   实验启示2：析构子类对象时，先调用子类析构函数，后调用父类析构函数
 6   实验启示3：在这个对象生命周期结束时，析构函数会自动调用
 7 
 8 
 9  */
10 
11 #include<iostream>
12 
13 int flag;
14 
15 class Animal
16 {
17 
18 public:
19 
20     int weight;
21     int length;
22     double hungry_rate;
23 
24     Animal(void);
25     ~Animal(){flag++;std::cout<<flag<<". I‘m ~Animal(),now."<<std::endl;}
26 
27     void eat(void);
28 
29 };
30 
31 Animal::Animal()
32 {
33     flag++;
34 
35     std::cout<<flag<<". I‘m Animal,now."<<std::endl;
36 
37     weight=25;
38     Animal::length=10;
39     Animal::hungry_rate=70;
40 
41 }
42 
43 void Animal::eat(void)
44 {
45 
46     std::cout<<"The Animal is eating"<<std::endl;
47 
48 }
49 
50 class Fish:public Animal
51 {
52 
53 public:
54 
55     Fish(){ flag++;std::cout<<flag<<". I‘m Fish,now."<<std::endl;}
56     ~Fish(){flag++;std::cout<<flag<<". I‘m ~Fish(),now."<<std::endl;}
57 
58     void swim()
59     {
60 
61         std::cout<<"The Fish Is Swimming!"<<std::endl;
62 
63     }
64 };
65 
66 int main()
67 {
68 
69     Fish x;
70 
71     x.eat();
72 
73     std::cout<<x.hungry_rate;
74 
75     x.swim();
76 
77     return 0;
78 }