在 C++ 中重载输入流我的解决方案有什么问题

Question

istream & read_person(istream & in, person * & p){
  char start, end, s, n, t, e = '[=10=]';
  string surname, name, tele, email, pers ="";
  if ((in >> start)&&(start =='<')) {
    if((in >> pers >> s >> surname >> n >> name >> end) && (start == '<' &&     pers == "person" && s == 'S' && n == 'N' && end == '>')) {
   person p_0(name,surname);
   p = &p_0;
}
else if((in >> pers >> s >> surname >> n >> name >> t >> tele >> end) && (start == '<' && pers == "person" && s == 'S' && n == 'N' && t == 'T'  && end == '>')
{
  person_with_telephone p_t(name, surname, tele);
  p = &p_t;
}
 else if((in >> pers >> s >> surname >> n >> name >> e >> email >> end) && (start == '<' && pers == "person" && s == 'S' && n == 'N' && e == 'E'  && end == '>'))
{
  person_with_email p_e(name, surname, email);
  p = &p_e;
}
else if((in >> pers >> s >> surname >> n >> name >> t >> tele >> e >> email >> end) && (start == '<' && pers == "person" && s == 'S' && t== 'T' && e == 'E' && n == 'N' && end == '>'))
{
  person_with_telephone_and_email p_t_e(name, surname, tele, email);
  p = &p_t_e;
    }
   else
     {
       in.setstate(ios::badbit); //read failed

     }
 }
 return in;
}

这是我的人 class 很容易理解它有名字和姓氏两个字符串和一个打印方法

class person
{
  string name;
  string surname;

  public:

  person(){}

  person(string strName, string strSurname):name(strName),surname(strSurname)  { }        

  void set_name(string strName)
  {    name= strName;  }

   void set_surname(string strSurname)
  {    surname= strSurname;  }

  string get_name()const
  {    return name;  }

  string get_surname()const
  {    return surname;  }

  virtual  bool has_telephone_p()const
  {    return false;  }

  virtual bool has_email_p()const
  {    return false;  }


  virtual void print(ostream& out)const
  {
           out << "<person S "<<get_surname()<<" N " << get_name() << ">";
   }    

    };

我正在尝试重载可以读取为这种格式的 iostream 第一个读起来很好，但其他情况下读起来不好

Answer 1

请不要为此使用指针。

person p_0(name,surname); // temporary person
p = &p_0; // assign its address to a pointer

p_0 最终超出范围。你留下了一个无效的指针和未定义的行为。

将 operator>> 签名更改为：

istream &read_person(istream &in, person &p); // no pointer here, just reference

并调整里面的代码：

p = p_0;                   // making a copy
p = person(name, surname); // you might as well do it in one line
p = {name, surname};       // or like this

不要在将来从惯用方法转向容易出错的方法。

在 C++ 中重载输入流我的解决方案有什么问题

overloading input stream in c++ what is wrong in my solution

c++

iostream

operator-overloading