cpp08.cpp

C++参考书

// Coded by plusir -- Jan.07.2002.
// Standard C++ Bible -- (P374-12-8)

#include <iostream>
using namespace std ;

class Date
{
	public:
		Date( int m = 0, int d = 0, int y = 0 )
		{
			month = m ;
			day = d ;
			year = y ;
		}

		void display( void ) const
		{
			cout << endl << month << '/' << day << '/' << year << endl ;
		}

	private:
		int month ;
		int year ;
		int day ;
} ;

class DatePtr
{
	public:
		DatePtr( Date *d = NULL )
		{
			dp = d ;
		}

		Date* operator -> ( void )
		{
			static Date nullDate( 0, 0, 0 ) ;
			if ( dp == NULL )
				return &nullDate ;
			return dp ;
		}

	private:
		Date *dp ;
} ;

int main()
{
	DatePtr dp ;
	dp->display() ;

	Date dt( 3, 17, 90 ) ;
	dp = &dt ;

	dp->display() ;

	return 0 ;
}