C + + Internal classes

An inner class is actually a kind of local data type defined within a class declaration.

Declarations of----inner classes are of public and private

If declared as public, it can also be used outside to define variables, such as Outer::inner var

If the declaration is private, then the outside can not be used to define the variable, then outer::inner var will cause a compilation error.

----the inner class is declared, it can be used to define the variable

This is the same as other data type definition variables, and access rules are the same. Without him

----Mutual access of internal classes and external classes

cannot be accessed and is completely dependent on the definition property of the member variable.

----For example

1 #include <iostream>
2 using namespace Std;
3
4 Class A
5 {
6 Public:
7 Class B1
8 {
9 Public:int A;
Ten Private:int B;
public:void foo (A &p) {
cout << p.i1 << Endl; OK, because I1 is public in class A
cout << p.i2 << Endl; Fail, because I2 is private in class A
14}
15};
16
+ Private:
Class B2
19 {
Public:int A;
Private:int b;
public:void foo (A &p) {
cout << p.i1 << Endl; OK, because I1 is public in class A
cout << p.i2 << Endl; Fail, because I2 is private in class A
25}
26};
27
Public:
B1 B11;
B2 B12;
I1 int;
Private:
B1 B21;
B2 B22;
I2 int;
Public:
PNS void F (b1& p) {
cout << p.a << Endl; OK, because a is public in class B1
cout << p.b << Endl; Fail, because B is private in class B1
40}
b2& void F (p) {
cout << p.a << Endl; OK, because a is public in class B2
cout << p.b << Endl; Fail, because B is private in class B2
44}
45};
46
int main (int argc, char *argv[])
48 {
A;
A::B1 AB1; OK, because B1 is declared as public inner class.
Wuyi A::B2 ab2; Fail, because B2 is declared as private inner class
return 0;
53}

http://blog.csdn.net/hihui/article/details/4822412

C + + Internal classes