c++ overloading operator<< and>>

Question

class Book
{ 
     string title;
     int category;
 public:
    Book(const string& abook, int num);
    string getTitle() const;
    int getCategory() const;
           


        

Answer 1

What should you put inside the overloaded << and >> operators?
Well, You can actually put anything inside the overloaded << and >> operator. They will just be simple function calls whenever a appropriate opportunity presents.
For eg:

Book obj;
cout<< obj;  //Calls your overloaded << operator

As a general principle while overloading operators you should follow Principle of Least Astonishment, which means your code should be doing something similar what the operator does for a intrinsic data type. In the above example I would expect my << operator to display the contents of my Book class, in that case I would overload it as follows:

// Display title and category 
ostream& operator<<(ostream& os, const Book& abook);
{
    os << abook.title << "\n";
    os << abook.category<< "\n";

    return os; // must return ostream object
}

I need to return a stream object since it allows for the chaining ex:

Book obj1,obj2,obj3;
cout<<obj1<<obj2<<obj3;

Similarly, for >> Extraction operator I would expect the operator to get the data from user. For ex:

Book obj;
cin>>obj; //Calls your overloaded >> operator

I would overload the >> operator as follows:

//Get the Book Title & Category from User
istream& operator>>(istream& is, Book& abook)
{
    cout << "Enter Book Title: ";
    is >> abook.title ;
    cout << "Enter Book Category: ";
    is >> abook.category;

    return is;  //Must return stream object
}

So, the bottomline is You can put any functionality inside >> and << operators but don't forget the Principle of Least Astonishment!