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 }

运行结果：