通过虚继承某个基类，就是在告诉编译器：从当前这个类再派生出来的子类只能拥有那个基类的一个实例。
虚继承的语法：
1 class Teacher:virtual public Person
2
3 {
4
5 }
这样做的话便可以让Student和Teacher类都虚继承自Person类，编译器将确保从Student和Teacher类再派生出来的子类只能拥有一份Person类的属性。
实例：虚继承应用
1 #include <iostream>
2 #include <string>
3 //虚继承可以让Student和Teacher类都虚继承自Person类，
4 //编译器将确保从Student和Teacher类再派生出来的子类只能拥有一份Person类的属性。
5 using namespace std;
6
7 #include <string>
8 //人类
9 class Person
10 {
11 public:
12 Person(string theName);//构造函数，theName为类的输入参数
13 void introduce();
14 protected:
15 string name;
16 };
17 Person::Person(string theName)//构造函数实现
18 {
19 name = theName;
20 }
21 void Person::introduce()//introduce()函数实现
22 {
23 cout << "大家好，我是" << name << "。\n\n";
24 }
25
26 //老师类继承于人类
27 class Teacher:virtual public Person//虚继承，再有类继承Teacher类时，将只拥有一份Person类的属性。
28 {
29 public:
30 Teacher(string theName,string theClass);
31
32 void teach();//教书
33 void introduce();
34 protected:
35 string classes;
36 };
37 Teacher::Teacher(string theName,string theClass):Person(theName)//老师的名字继承于人类中的名字
38 {
39 classes = theClass;
40 }
41 void Teacher::teach()
42 {
43 cout<< name << " 教 "<< classes << "。\n\n";
44 }
45 void Teacher::introduce()
46 {
47 cout<<"大家好，我是 "<< name <<" ，我教 "<< classes << "。\n\n";
48 }
49
50 //学生类继承于人类
51 class Student:virtual public Person//虚继承，再有类继承Student类时，将只拥有一份Person类的属性
52 {
53 public:
54 Student(string theName,string theClass);
55
56 void attendClass();//要上课
57 void introduce();
58 protected:
59 string classes;
60 };
61 Student::Student(string theName,string theClass):Person(theName)//学生名字继承于人类中的名字
62 {
63 classes = theClass;
64 }
65 void Student::attendClass()
66 {
67 cout<< name <<"加入"<< classes << "学习。\n\n";
68 }
69 void Student::introduce()
70 {
71 cout<< "大家好，我是" << name << "，我在" << classes << "学习。\n\n";
72 }
73
74 //助教类既继承于老师类，又继承于学生类
75 class Assistant:public Teacher,public Student
76 {
77 public:
78 Assistant(string theName,string classTeaching,string classAttending);
79
80 void introduce();
81 };
82 Assistant::Assistant(string theName,string classTeaching,string classAttending)
83 :Teacher(theName, classTeaching),Student(theName,classAttending),Person(theName)
84 //由于虚继承，Teacher和Student都不能拥有Person类中的属性和方法
85 //只能由Person类自己给出
86 {
87 //多继承 助教既继承老师类，又继承学生类
88 }
89 void Assistant::introduce()
90 {
91 cout << "大家好，我是" << Student::name << ".我教" << Teacher::classes << "，";
92 cout << "同时我在" << Student::classes << "学习。\n\n";
93 }
94
95 int main()
96 {
97 Teacher teacher("小甲鱼","C++入门班");
98 Student student("迷途羔羊","C++入门班");
99 Assistant assistant("丁丁","C++入门班","C++进阶班");
100
101 teacher.introduce();
102 teacher.teach();
103
104 student.introduce();
105 student.attendClass();
106
107 assistant.introduce();
108 assistant.teach();
109 assistant.attendClass();
110
111 return 0;
112 }
