Thread: Overloaded stream insertion study

I'm trying to convert this simple phone number program into a demonstration of using the overloaded stream-insertion operator as a member function, i.e. I'm trying to use

Code:

 phone << cout

instead of the typical

Code:

 cout << phone

Can someone point me in the right direction?

Code:

#include <iostream>
#include <iomanip>

using namespace std;

class PhoneNumber {
   ostream &operator<<( ostream& ); // defined as a member function
   friend istream &operator>>( istream&, PhoneNumber& );

private:
   char areaCode[ 4 ]; // 3-digit area code and null
   char exchange[ 4 ]; // 3-digit exchange and null
   char line[ 5 ];  // 4-digit line and null

ostream &operator<<( ostream &output ) // defined as a member function
{
   output << "(" << num.areaCode << ")" << num. exchange << "-" << num.line;

   return output; // enables cout << a << b << c;
} // end function operator<<



}; // end class PhoneNumber

istream &operator>>( istream &input, PhoneNumber &num )
{
   input.ignore();
   input >> setw( 4 ) >> num.areaCode;
   input.ignore( 2 ); // skip ( and space
   input >> setw( 4 ) >> num.exchange;
   input.ignore();
   input >> setw( 5 ) >> num.line;  // input line

   return input;
}

int main()
{
   PhoneNumber phone; // create object phone

   cout << "Enter phone number in the form (123) 456-7890:\n";

   cin >> phone; // operator>>(cin, phone)

   cout << "The phone number entered was: ";

  //cout << phone << endl; // operator<<( cout, phone );

    phone << cout << endl;
    phone.operator<<( cout ); // must be defined within the function operator<<

   return 0;
} // end main

Simply change the order of the parameters in the overloaded operator.

Code:

#include <iostream>
#include <iomanip>

using namespace std;

class myClass {
   friend ostream &operator<<(const myClass&, ostream&);
   int data;
   public:
     myClass(int d) : data(d) {}
};

ostream &operator<<(const myClass& obj, ostream& file) {
    return file << obj.data;
}

int main()
{
   myClass obj1(5);
   
   obj1 << cout;
   cin.get();
   return 0;
}

Now keep in mind, there is no way to prevent the right shift operator from reading left to right, so chaining becomes impossible without a reference to the ostream, for instance

Code:

obj1 << obj1 << cout; // Doesn't work

You also can't, as you seem to be trying to do, make it a member function. It's simply not allowed in the language to change the number of arguements.