static member function error in c++

Question

If static class member and static class function has a class scope then why can't I access the display function(it shows error)? If in place of display function I write count it displays the correct value i.e., 0

#include <iostream>
#include <string> 

using namespace std;

class Person
{
    public:
     static int Length;
     static void display()
     {
        cout<< ++Length;
     }
};

int Person::Length=0;

int main()
{
   cout<< Person :: display(); //error
   // Person :: Length shows correct value
   return 0;
}

TartanLlama · Accepted Answer · 2015-03-31 14:12:43Z

5

You can call the display function, your error is that you are trying to output the result to cout. Person::display doesn't return anything, hence the error.

Just change this:

cout<< Person :: display(); //error

To this:

Person::display();

answered Mar 31, 2015 at 14:12

TartanLlama

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2 Comments

Stack Over a year ago

but why does it work with the static members and not with the static member function? cout<<Person :: Length prints correct value

TartanLlama Over a year ago

Because Person::Length is an int. Person::display() returns nothing. You can't output nothing.

Giulio Franco · Accepted Answer · 2015-03-31 15:27:57Z

0

If you want to pipe objects into streams, you need to define an appropriate operator <<, like this:

#include <iostream>
#include <string> 

using namespace std;

class Person
{
    public:
     class Displayable {
         template< typename OStream >
         friend OStream& operator<< (OStream& os, Displayable const&) {
             os << ++Person::Length;
             return os;
         }
     };
     static int Length;
     static Displayable display() { return {}; }
};

int Person::Length=0;

int main()
{
   cout<< Person :: display(); //works
   // Person :: Length shows correct value
   return 0;
}

answered Mar 31, 2015 at 15:27

Giulio Franco

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