Question

所以我差不多完成了这个，我无法弄清楚我需要在我的重载输出操作符中返回什么。最初它的返回次数减少了，但我一直得到错误（类型＆＃34的引用; std :: ostream＆amp;＆＃34;（不是const限定）不能用类型＆＃34;的值初始化。 bool＆＃34;）在我的回复声明中我需要做什么？

class Student
{
 private:
    int stuID;
    int year;
    double gpa;
 public:
    Student(const int, const int, const double);
    void showYear();
    bool operator<(const Student);
 friend ostream& operator<<(ostream&, const Student&);
};
Student::Student(const int i, int y, const double g)
{
   stuID = i;
   year = y;
   gpa = g;
}
void Student::showYear()
{
   cout << year;
}
ostream& operator<<(ostream&, const Student& otherStu)
{
   bool less = false;
   if (otherStu.year < otherStu.year)
     less = true;
     return ;
}
int main()
{
    Student a(111, 2, 3.50), b(222, 1, 3.00);
    if(a < b)
   {
      a.showYear();
      cout << " is less than ";
      b.showYear();
   }
   else
   {
     a.showYear();
     cout << " is not less than ";
     b.showYear();
   }
  cout << endl;
  _getch()
  return 0;
 }

Answer 1

听起来你在operator<和operator<<之间感到困惑。

// operator< function to compare two objects.
// Make it a const member function
bool Student::operator<(const Student& other) const
{
   return (this->year < other.year);
}

// operator<< function to output data of one object to a stream.
// Output the data of a Student
std::ostream& operator<<(std::ostream& out, const Student& stu)
{
   return (out << stu.stuID << " " << stu.year << " " << stu.gpa);
}

Answer 2

根据这里的文件：

http://en.cppreference.com/w/cpp/language/operators

您需要返回参数中的ostream ..

std::ostream& operator<<(std::ostream& os, const Student& obj)
{

    return os << obj.stuID << ", " << obj.year << ", " << obj.gpa;
}

决定返回什么 - bool值

2 个答案: