C++嵌套类

C++支持类的嵌套，其语法比较简单。代码是最好的说明。

 1 #include <iostream>
 2 using namespace std;
 3 
 4 class Outter{
 5     public:
 6         int a;
 7         static int s;
 8         //nested class and enclosing class are independent.
 9         class Inner{ 
10             public:
11             int b;
12             //nested class can access static members of enclosing class
13             int foo(){ return b + s;}
14             int bar();
15         };
16 };
17 
18 int Outter::s = 1;
19 //define a nested class member outside of the class declaration.
20 int Outter::Inner::bar(){
21     return 0xdeadbeef;
22 }
23 
24 int main(){
25     Outter o;
26     o.a = 0;
27     //if nested class is specified as public, then everyone can use the nested class.
28     //if nested class is specified as protected, then only the enclosing class,
29     //friend of the enclosing class and derived class of the enclosing class can access the nested class.
30     //if the nested class is specified as private, then only the enclosing class
31     //and friend of the enclosing class can access the nested class.
32     Outter::Inner i;
33     i.b = 1;
34     cout<<i.foo()<<endl;
35     cout<<hex<<i.bar()<<endl;
36     return 0;
37 }