c++ - 重载 >> 继承类的运算符

Question

我将如何进行这项工作？教授指导我们使用私有(private)变量。我是否必须设置新变量以在 Student 构造函数中输入 Person 的私有(private)成员？使这项工作最有效的方法是什么？

提前谢谢你。

class Person
{
    friend istream& operator>>(istream&, Person&);
    friend ostream& operator<<(ostream&, Person&);
private:
    char* m_name;
    int m_age;
    string m_ssn;
public:
    Person() = default;
    Person(char*, int, const string&);
    Person(const Person&);
    ~Person();
    void setName(char*);
    char* getName();
    void setAge(int);
    int getAge();
    void setSSN(string);
    string getSSN();
    Person& operator=(const Person&);
};

// ...

class Student : public Person
{
    friend istream& operator>>(istream&, Student&);
    friend ostream& operator<<(ostream&, Student&);
private:
    float m_gpa;
public:
    Student() = default;
    Student(char*, int, const string&, float);
    Student(const Student&);
    void setGPA(float);
    float getGPA();
    Student& operator=(const Student&);
};

istream& operator>>(istream &is, Student &iStudent)
{
    // ?

    return is;
}

Answer 1

1. 实现 operator>>和 operator<<使用基类。
2. 使用virtual重定向实现的成员函数。

class Person
{
    friend std::istream& operator>>(std::istream&, Person&);
    friend std::ostream& operator<<(std::ostream&, Person&);

    ....

   public:

    virtual std::istream& read(std::istream&) { ... }
    virtual std::ostream& write(std::ostream&) const { ... }

    ...
};

std::istream& operator>>(std::istream &is, Person& person)
{
   return persone.read(is);
}

std::stream& operator<<(std::ostream &os, Person const& person)
{
   return persone.write(os);
}

class Student : public Person
{
   ...

   public:

    virtual std::istream& read(std::istream&) { ... }
    virtual std::ostream& write(std::ostream&) const { ... }

   ...
};