从 int 类型的右值初始化 &分数类型的非常量引用无效？

invalid initialization of non-const reference of type &Fraction from rvalue of type int?

本文关键字：类型 常量 非常 引用 无效 int 初始化      更新时间：2023-10-16
#include <iostream>
#include <utility>
using namespace std;
using namespace rel_ops;
class Fraction
{
private:
  //variables to store numerator and denominator
  int num;
  int denom;
public:
  Fraction(){}
  Fraction(int num): num(num) {}
  Fraction(int num, int denom): num(num), denom(denom) {}
  void set_num(int n){ num = n;}
  void set_denom(int d){ denom = d;}
  int get_numerator() const {return num;}
  int get_denominator() const {return denom;}
  Fraction &operator+= (const Fraction &obj){
    if (denom == obj.denom){
      return num + obj.num;
    }
  }
};
  //calculating highest common denominator
  int g_c_d(int n, int d){
    return d == 0? n : g_c_d(d, n % d);
 }
istream &operator>> (istream &input, Fraction &f)
{
  int n, d;
  char slash;
  input >> n;
  input >> slash;
  input >> d;
  if (d == 0) {n = 0;} //if denom is 0; fraction = 0/0
  f = Fraction(n, d);
  return input;
}
ostream &operator<<(ostream &output, const Fraction &frac)
{
  return output << frac.get_numerator() << "/" << frac.get_denominator();
}

int main()
{
   int n, d;
   Fraction frac;
   Fraction frac1(3,4);
   Fraction frac2(4,4);
   cout << frac1 << " + " << frac2 << " = ";
   cout << (frac1 += frac2) << endl;
   cout << "Enter a fraction" << endl;
   cin >> frac;  //user inputs fraction      
   n = frac.get_numerator();  //get users numerator
   d = frac.get_denominator();  //get users denominator
   gcd = g_c_d(frac.get_numerator() , frac.get_denominator());  //calculate gcd of     fraction using users input
   //set new simplified values for the users fraction
   frac.set_num(n/gcd);
   frac.set_denom(d/gcd);
   cout << "your fraction is: ";
   cout << frac << endl;
   return 0;
}
我

正在尝试添加两个分数，这些分数来自我自己定义的类。但是我收到此错误：从 in 类型的右值初始化 &Fraction 类型的非常量引用无效。

我重载了其他运算符，如"=="，它工作正常，但"+="不起作用。

您的operator +=返回一个临时的，它应该是这样的：

Fraction &operator+= (const Fraction &obj){
   if (denom == obj.denom){
      num += obj.num;
    } else {
        // you have also to do that part
    }
    return *this; // return this object, not a temporary
}
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