C++

12.5    An Output Like Any Other

The next step is actually just cosmetic. To output an object to an ostream, there is a commonly used method in practice: overload the operator<< global operator for ostream& and your type.

std::ostream& Person::print(std::ostream& os) {    return os << format("{} ({}) from {}", name_, age_, city_);}std::ostream& operator<<(std::ostream& os, Person p) {    return p.print(os);}  

Listing 12.9     You can overload the standard operator for output.

Instead of calling p.print(), you can also output the fields directly:

std::ostream& operator<<(std::ostream& os, Person p) {    return os << format("{} ({}) from {}", p.name_, p.age_,  p.city_);}  

Did you notice that the return type is not void? By returning the ostream passed as ...