流重载

2008-03-20 12:53:33 161 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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我现在想用流重载输出CDate类,如果我把实现放在Date.cpp或main函数文件里,就没有问题
但是如果我把实现放在Date.h文件下就会出问题。

如果我这样写：

#include <iostream>

using namespace std;





#if !defined(AFX_DATE_H__91F06C7A_00D0_410C_86AE_0C76D3E71326__INCLUDED_)

#define AFX_DATE_H__91F06C7A_00D0_410C_86AE_0C76D3E71326__INCLUDED_



#if _MSC_VER > 1000

#pragma once

#endif // _MSC_VER > 1000



class CDate  

{

	friend ostream& operator<<( ostream&, const CDate& );

public:

	CDate(int = 2008, int = 1 ,int = 1);

	CDate(const CDate &);

	void setDate(int, int, int);

	void setYear(int );

	void setMonth( int );

	void setDay ( int );

	int getYear() const;

	int getMonth() const;

	int getDay() const;

	bool isLeapYear( int ) const;

	void nextDay();

	virtual ~CDate();

private:

	int year, month, day;

	int checkDays( int, int , int);



};

ostream& operator<< ( ostream& output, const CDate& d)

{

	output<< "Year: " << d.getYear() << " Month: " << d.getMonth() << " Day: " << d.getDay() << endl;

	return output;

}

提示错误：这一行 cout << birthday;错误error C2593: 'operator <<' is ambiguous

如果我单写using std::ostream;
using std::cout;
using std::endl;
也在.h文件中，错误：
Student.obj : error LNK2005: "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class CDate const &)" (??6@YAAAV?$basic_ostream@DU?$char_traits@D@std@@@
std@@AAV01@ABVCDate@@@Z) already defined in Date.obj
Test_CStudent_main.obj : error LNK2005: "class std::basic_ostream<char,struct std::char_traits<char> > & __cdecl operator<<(class std::basic_ostream<char,struct std::char_traits<char> > &,class CDate const &)" (??6@YAAAV?$basic_ostream@DU?$char_trai
ts@D@std@@@std@@AAV01@ABVCDate@@@Z) already defined in Date.obj
Debug/Test_CStudent.exe : fatal error LNK1169: one or more multiply defined symbols found

麻烦高手给解释一下这两种错误是什么原因还有为什么会造成这两种错误。

...全文