C function problem-CodePudding

Pass the program, what circumstance, please advice

 
# include 
using namespace std; 
The class CDate;//class reference in advance statement 


The class CTime 
{
Public: 
CTime (int h, m int, int) s: hour (h), minute (m), second (s) {} 
Friend void CDate: : display (CTime t);//declare the CDate display function as friend yuan 
Void the display () 
{
cout} 
Private: 
Int hour; 
Int minute; 
Int second; 
}; 
The class CDate 
{
Public: 
CDate (int y, int m, int d) : the year (y), month (m), date (d) {} 
Void the display (CTime t) 
{
T.d isplay (); 
cout} 
Private: 
Int year; 
Int the month; 
Int the date; 
}; 

Int main () 
{
CTime t,11,11 (11); 
CDate d (12,12,12); 
D.d isplay (t); 
system("pause"); 
return 0; 
}

CodePudding user response:

I think you are understanding of a friend is not quite right,
Void display CTime (t)//use the parameter t, t.d isplay () call don't need a friend
The class is not used in CTime CDate: : the display, so a friend declaration is unnecessary

CodePudding user response:

reference 1st floor u010165006 response:

I think your understanding of a friend is not quite right,
Void display CTime (t)//use the parameter t, t.d isplay () call don't need a friend
The class is not used in CTime CDate: : display, so a friend declaration is redundant

I'm wrong, should be the CDate: : display and not have access to the class private or protected member CTime, so a friend declaration is superfluous,
-- -- -- -- -- --
Feel the case is not very suitable for use of a friend, if you want to use, I this also can change:

 # include 
using namespace std; 
The class CDate;//class reference in advance statement 


The class CTime 
{
Public: 
CTime (int h, m int, int) s: hour (h), minute (m), second (s) {} 
//friend void CDate: : display (CTime & amp; T);//declare the CDate display function as friend yuan 
Friend class CDate; 
Void the display () 
{
cout} 
Private: 
Int hour; 
Int minute; 
Int second; 
}; 
The class CDate 
{
Public: 
CDate (int y, int m, int d) : the year (y), month (m), date (d) {} 
Void the display (CTime & amp; T) 
{
//t.d isplay (); 
coutcout} 
Private: 
Int year; 
Int the month; 
Int the date; 
}; 

Int main () 
{
CTime t,11,11 (11); 
CDate d (12,12,12); 
D.d isplay (t); 
system("pause"); 
return 0; 
}

I use VC6.0 and VC2010 Express edition,
//friend void CDate: : display (CTime & amp; T);//can't
Friend class CDate;//can
I don't know why?

CodePudding user response:

Appropriate adjust the code sequence,

 # include 
using namespace std; 
The class CTime.//class reference in advance statement 

The class CDate 
{
Public: 
CDate (int y, int m, int d) : the year (y), month (m), date (d) {} 
Void the display (CTime & amp; T); 
Private: 
Int year; 
Int the month; 
Int the date; 
}; 

The class CTime 
{
Public: 
CTime (int h, m int, int) s: hour (h), minute (m), second (s) {} 
Friend void CDate: : display (CTime & amp; T);//declare the CDate display function as friend yuan 
Void the display () 
{
cout} 
Private: 
Int hour; 
Int minute; 
Int second; 
}; 

Void CDate: : display (CTime & amp; T) 
{
//t.d isplay (); 
coutcout} 

Int main () 
{
CTime t,11,11 (11); 
CDate d (12,12,12); 
D.d isplay (t); 
system("pause"); 
return 0; 
}

CodePudding user response:

Thank you