Question

我需要帮助为类调试此代码。我不是计算机科学专业，所以我需要用非常基本的术语来解释。我得到的错误代码是错误LNK2019：未解析的外部符号“public：void __thiscall Student :: showStudent（void）”（？showStudent @ Student @@ QAEXXZ）在函数_main中引用

我不明白这意味着什么。有人可以解释一下吗？

#include<iostream>
#include<string.h>

using namespace std;
//Added namespace
class Person
{
public:
char initial;
Person(const int id, const int a, const char i);
//Renamed function Person
void showPerson();
int idNum;
int age;
};

Person::Person(const int id, const int a, const char i)
{
idNum = id;
age = a;
initial = i;
};
void Person::showPerson(void)
{
cout << "Person id#: " << idNum << " Age: " << age << " Initial: " << initial;
//Added << to the correct places
}
class Student
{
public:
Student (const int id, const int a, const char i, const double gpa);
void showStudent();
double gpa;
int idNum;
int age;
char initial;
};
Student::Student(const int id, const int a, const char i, const double gradePoint)
{
Person::Person(id, a, i);
gpa = gradePoint;
};

void showStudent(Student student)
{
cout << "Student ID# " << student.idNum;
cout << " Avg: " << student.gpa << endl;
cout << "Person id#: " << student.idNum << " Age: " << student.age << " Initial: " << student.initial;
cout << endl << " Age: " << student.age << ".";
cout << " Initial: " << student.initial << endl;
};
void main()
{
Person per(387, 23, 'A');
//Put two lines into one
cout << endl << "Person..." << endl;
per.showPerson();
Student stu(388, 18, 'B', 3.8);
cout << endl << endl << "Student..." << endl;
stu.showStudent();
system("pause");
}

它给我一个LNK2019错误？求救！

Answer 1

添加到AndyG的答案。您的Student类应该继承自Person。像这样：

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

因为在您的学生构造函数中，您正在调用Person::Person(id, a, i);并且这不会设置您的Student属性idNum, age and initial，因为您已在学生中重新定义了这些属性，而您＃＆＃ 39;重新调用Person ctor而不将其初始化为任何内容。

为了使您的代码更具凝聚力和可重用性，我将定义如下类：

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();

};

通过这种方式，您的Student个实例拥有Person类中的所有受保护成员属性（id，age和initial），这定义了Student 是< / strong> Person。这是面向对象编程（OOP）范例的一部分。

所以你设置这样的学生构造函数：

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; };

现在你不应该有错误，而且你手边有一个干净，可重复使用的OOP解决方案。例如，您现在可以拥有一位教师，该教师也从Person继承（是一种概括），并且具有Person的属性。

错误代码LNK2019

1 个答案:

为了使您的代码更具凝聚力和可重用性，我将定义如下类：