C ++中的重载ostream运算符错误

Question

我尝试在 class 学生中重载 ostream 运算符，如下所示：

//Student.h
class Student
{
    public:
        Student(){}
        ~Student(){}
        friend std::ostream& operator<< (std::ostream&,const Student&);
        friend std::istream& operator>> (std::istream&,const Student&);
    private:
        char* snum;
};

//Student.cpp
#include "Student.h"
std::ostream& operator<< (std::ostream& output,const Student& c)
{
    output<<c.snum<<", "<<c.name<<", "<<c.email<<endl;
    return output;
}
std::istream& operator>> (std::istream& input,const Student& cN)
{
    cout<<"Input number: ";
    input>>cN.snum;
    return input;
}

//main.cpp
#include "Student.h"
int main() 
{
    Student st;
    std::cin >> st;
    std::cout << st << std::endl;
    return 0;
}

但是当我输入 snum 时，我收到错误消息 "Segmentation Fault"。我将 char* snum; 更改为 char snum;，它 return 编译器错误 The operation "std::istream>> const char" is illegal. 谢谢你的帮助。

Answer 1

你需要snum指向分配内存，然后你可以输入数据，例如：

   char* p_var = new char[20]; // 20 bytes allocation 

   // ... using p_var

   delete[] p_var; // Releasep_var memory

在你的情况下，你应该在Ctor中进行分配，在Dtor中进行释放。您可以阅读此内容以获取更多信息： http://www.cplusplus.com/doc/tutorial/basic_io/

Answer 2

如果您的问题通过以下更改得到解决，请告诉我...

class Student
{
     private:
        char snum;
        char name;
        char email;
    public:
        Student(){};
        ~Student(){};
        friend std::ostream& operator<< (std::ostream&,Student&);
        friend std::istream& operator>> (std::istream&,Student&);

};


std::ostream& operator<< (std::ostream& output,Student& c)
{
    output<<c.snum<<", "<<c.name<<", "<<c.email<<endl;
    return output;
}
std::istream& operator>> (std::istream& input, Student& cN)
{
    cout<<"Input number: ";
    input>>cN.snum;
    input>>cN.name;
    input>>cN.email;
    return input;
}


int main() 
{
    Student st;
   std::cin >> st;
    std::cout << st << std::endl;
    return 0;
}

在用于 cin 之前使用字符串或字符数组或为 char *x 分配一些内存...

C ++中的重载ostream运算符错误

Overloaded ostream operator error in c++

c++

operator-overloading