c++派生类中构造函数和析构函数执行顺序、判断对象类型、抽象类、虚函数

                 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<algorithm>
 4 #include<iostream>
 5usingnamespace std;
 6class A
 7{
 8public:
 9int a,b;
10    A();
11     A(int x,int y);
12     ~A();
13};
14A::A()
15{
16     printf("调用A类构造函数\n");
17}
18 A::A(int x,int y)
19{
20     a=x;
21     b=y;
22     printf("调用A类构造函数\n");
23}
24 A::~A()
25{
26     printf("调用A类析构函数\n");
27}
28class B:public A
29{
30public:
31int aa,bb;
32    B()
33    {
34         printf("调用B类构造函数\n");
35    }
36     B(int x,int y)
37    {
38         aa=x;
39         bb=y;
40         printf("调用B类构造函数\n");
41    }
42     ~B()
43    {
44         printf("调用B类析构函数\n");
45    }
46};
47class C:public B
48{
49public:
50int aaa,bbb;
51    B one;
52     C(int x,int y)
53    {
54         aaa=x;
55         bbb=y;
56         one.aa=x;
57         one.bb=y;
58         printf("调用C类构造函数\n");
59    }
60     ~C()
61    {
62         printf("调用C类析构函数\n");
63    }
64};
65int main()
66{
67     C first(0,0);
68     printf("%d %d %d %d\n",first.aaa,first.bbb,first.one.aa,first.one.bb);
69return0;
70 }

                  1 #include<stdio.h>
  2 #include<string.h>
  3 #include<algorithm>
  4 #include<iostream>
  5usingnamespace std;
  6class Base
  7{
  8public:
  9     Base(int x,int y)
 10    {
 11         a=x;
 12         b=y;
 13    }
 14virtualvoid show()  //声明了虚函数，那么指针指向哪个对象就用那个对象的函数 15     {     //否则的话，声明指针是什么类型就会用那个类型的函数 16         cout<<"基类内容show打印"<<endl;
 17         cout<<"a:"<<a<<"b:"<<b<<endl;
 18    }
 19void prinf()
 20    {
 21         cout<<"基类内容prinf打印"<<endl;
 22         cout<<"a:"<<a<<"b:"<<b<<endl;
 23    }
 24private:
 25int a,b;
 26 27};
 28class One:public Base
 29{
 30public:
 31 32     One(int x,int y):Base(x,y)
 33    {
 34         aa=x;
 35         bb=y;
 36    }
 37void show()
 38    {
 39         cout<<"派生类内容show打印"<<endl;
 40         cout<<"aa:"<<aa<<"bb:"<<bb<<endl;
 41    }
 42void prinf()
 43    {
 44         cout<<"派生类内容prinf打印"<<endl;
 45         cout<<"aa:"<<aa<<"bb:"<<bb<<endl;
 46    }
 47private:
 48int aa,bb;
 49};
 50int main()
 51{
 52     Base mb(100,200),*pc;
 53     One mc(200,300);
 54     pc=&mc;
 55     pc->show();
 56     pc->prinf();
 57     pc=&mb;
 58     pc->show();
 59     pc->prinf();
 60return0;
 61}
 62 63//2、 64 #include<stdio.h>
 65 #include<string.h>
 66 #include<algorithm>
 67 #include<iostream>
 68usingnamespace std;
 69class Shape   //抽象类定义是只要里面有一个纯虚函数那他就是抽象类， 70 {   //抽象类不需要什么关键字来定义，且它的派生类必须覆盖重写他的纯虚方法 71public :
 72double a;
 73     Shape(double x)
 74    {
 75         a=x;
 76    }
 77virtualvoid area()=0;
 78virtualvoid show()=0;
 79};
 80class Circle:public Shape
 81{
 82public:
 83     Circle(double x):Shape(x)
 84    {
 85 86    }
 87void area()
 88    {
 89         cout<<"the circle area is :"<<endl;
 90         cout<<3.14*a*a<<endl;
 91    }
 92void show()
 93    {
 94         cout<<"a:"<<a<<endl;
 95    }
 96};
 97int main()
 98{
 99     Shape *ptr;
100     Circle r(6);
101     ptr=&r;
102     ptr->area();
103     ptr->show();
104return0;
105}
106107//3、108 #include<stdio.h>
109 #include<string.h>
110 #include<algorithm>
111 #include<iostream>
112 #include<typeinfo>
113usingnamespace std;
114class Sqare
115{
116public :
117double a;
118     Sqare(double x)
119    {
120         a=x;
121    }
122};
123class Circle
124{
125public :
126double a;
127     Circle(double x)
128    {
129         a=x;
130    }
131};
132int main()
133{
134     Sqare one(1);
135     Circle two(2);
136if(typeid(one)==typeid(Sqare))  //判断对象类型137    {
138         cout<<"它是Sqare对象"<<endl;
139    }
140else141    {
142         cout<<"它是Circle对象"<<endl;
143    }
144145if(typeid(two)==typeid(Sqare))
146    {
147         cout<<"它是Sqare对象"<<endl;
148    }
149else150    {
151         cout<<"它是Circle对象"<<endl;
152    }
153return0;
154 }