c++ - 错误代码 LNK2019

Question

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Answer 1

添加到 AndyG的回答。您的 Student 类应该继承自 Person。像这样:

class Student : public Person {
 /* members */
};

因为在您的 Student 构造函数中您正在调用 Person::Person(id, a, i); 并且这不会设置您的 Student 属性 idNum , age 和 initial，因为您已经在 Student 中重新定义了它们，并且您在调用 Person ctor 时没有将其初始化为任何东西。

为了使您的代码更具凝聚力和可重用性，我会这样定义类:

class Person {
      protected:
        char initial;
        int idNum;
        int age;
      public:
        Person(const int id, const int a, const char i);
        void showPerson();

};

class Student : public Person {
      private:
        double gpa;
      public:
        Student (const int id, const int a, const char i, const double gpa);
        void showStudent();

};

In this way your Student instances have all of the protected member attributes (id, age and initial) from the Person class and this defines a Student is a Person. This is part of Object Oriented Programming (OOP) paradigm.

所以你像这样设置你的 Student 构造函数:

Student::Student(const int& id, const int& a, const char& i, const double& gradePoint) {
    idNum = id; // This works because Student inherits from Person, so it has all its attributes!
    age = a;
    initial = i;
    gpa = gradePoint;
}; 

现在您不应该有错误，并且您手头有一个干净、可重用的 OOP 解决方案。例如，您现在可以拥有一个也从 Person 继承(泛化)的 Teacher，并且它将具有 Person 的属性。