/* 本程序來自thinking in c++ P463 頁
* 本程序是為了說明拷貝構造函數也是一個構造函數，以及什么時候調用拷貝構造
* 函數.
* 本程序設計的類的功能就是在任意時刻都能知道屬于該類的對象的個數。顯然是
*用static member data實現的
*/
#include <fstream>
#include <string>
using namespace std;
ofstream out("HowMany.out");

class HowMany {
	string m_name;            //object identifier
	static int s_objectCount;
public:
	HowMany( const string &id = "") : m_name(id){
		++s_objectCount;
		print("HowMany()");
	}

	~HowMany() {
		-- s_objectCount;
		print("~HowMany()");
	}

	HowMany( const HowMany &h) : m_name( h.m_name ){
        m_name += " copy";
		++s_objectCount;
		print("HowMany( const HowMany &)");
	}

	void print( const string &msg = "" )const {
		if(msg.size() != 0)
			out << msg << endl;
		out << '\t' << m_name << ":" << "s_objectCount" << s_objectCount << endl;