32 C++ - 运算符重载碰上友元函数

class Person{
  friend ostream& operator<<(ostream& os, Person& person);
  public:
    Person(int id,int age){
      mID = id;
      mAge = age;
    }
  private:
    int mID;
    int mAge;
};
ostream& operator<<(ostream& os, Person& person){
  os << "ID:" << person.mID << " Age:" << person.mAge;
  return os;
}
int main(){
  Person person(1001, 30);
  //cout << person; //cout.operator+(person)
  cout << person << " | " << endl;
  return EXIT_SUCCESS;
}