类的嵌套定义，使用

/* objcount.cpp
*类的嵌套，此例可以跟踪程序在任何时候
*有多少该类型的对象
*/
#include <iostream>

using namespace std;

class TAnyClass {
private:
    typedef int CLASS_COUNTER;
    static CLASS_COUNTER ClassCount;
    static int GetCount() { return ClassCount; }
public:
    TAnyClass() { ClassCount++; }
    ~TAnyClass() { ClassCount --; }
    static void ShowCount();
    struct ClassStruct {
        int x, y;
        };
};

//Define static member
TAnyClass::CLASS_COUNTER TAnyClass::ClassCount;
TAnyClass globalObject;

int main()
{
    cout << "On entry to program" << endl;
    TAnyClass::ShowCount();

    TAnyClass localObject;
    cout << "After constructing one object" << endl;
    TAnyClass::ShowCount();

    TAnyClass objectA, objectB, objectC;
    cout << "After constructing three objects" << endl;
    TAnyClass::ShowCount();

    TAnyClass * pointer = new TAnyClass;
    cout << "After creating a dynamic object" << endl;
    TAnyClass::ShowCount();
    delete pointer;
    cout << "After deleting the dynamic object" << endl;
    TAnyClass::ShowCount();

    //引用结构体
    TAnyClass::ClassStruct structure;
    structure.x = 1;
    cout << "y == " << structure.y << "x == " << structure.x
         << endl;

    return 0;
}

void TAnyClass::ShowCount()
{
    cout << "Number of objects == " << TAnyClass::GetCount();
    cout << endl;
}

类的内部嵌套定义  typedef int CLASS_COUNTER；还有一个示例结构体 struct ClassStruct
及静态类，静态变量不和对象捆绑使用，且不会接收this指针。。



一些不常用的关键字：
implicit:强制调用所需的类构造器，拒绝C++隐式转换成类型
mutable: 类内部函数声明对成员变量不修改时，如:int getvalue()const { counter ++; } 这时编译会报错，
         此时在变量前加上此关键字，允许函数修改此单个变量。