C ++构造函数问题//继承的类

Question

Initial problem solved. (which was a redefinition error)

Furthermore, I don't know how to create a Student constructor which delivers the following:

This is how I want my program / constructors to work:

//main.cpp
Student s1(4015885);
s1.print();
Student s2("Test", "Student", 22, 5051022);
s2.print();

The output should be as follows:

Standart
Name
18
4015885

Test
Student
22
5051022

s1 works, but s2 doesn't work, because I don't have a fitting constructor

This is my Person.h

#pragma once
#include <iostream>
#include <string>
using namespace std;

class Person {

public:
    Person(string name = "Standard", string surname =  "Name", int age**strong text** = 18);                              

    //GET
    //SET
    void print();

protected:
    string name, surname;
    int age;
};

Person.cpp

#include <iostream>
#include <string>
#include "Person.h"
using namespace std;

Person::Person(string n, string s, int a) : name(n), surname(s), age(a)
{
    cout << "Person constructor" << endl;
}
void Person::print() {
    cout << name << endl << surname << endl << age << endl << endl;
}

Student.h

#pragma once
//#ifndef PERSON_H
//#define PERSON_H
#include "Person.h"

class Student : public Person {
public:

    Student(int matrikel_nummer);

    int get_matriculation_number();

    void set_matriculation_number(int matriculation_number) {
        this->matriculation_number = matriculation_number;
    }

    void print();

private:
    int matriculation_number;

};
//#endif

Student.cpp

#include <iostream>
#include <string>
#include "Student.h"
using namespace std;

Student::Student(int matrikel_nummer) : Person(name, surname, age)

{
    cout << "Student constructor" << endl;
    this->matriculation_number = matriculation_number;
}

void Student::print() {
    cout << name << endl
            << surname << endl
            << age << endl 
            << matriculation_number << endl << endl;
}

Answer 1

In Student.h you have

Student(int matriculation_number) : Person(name, surname, age){};

Which declares and defines a constructor for Student . Then in Student.cpp you have

Student::Student(int matrikel_nummer) : Person(vorname, nachname, alter)

{
    cout << "Student constructor" << endl;
    this->matrikel_nummer = matrikel_nummer;
}

Which redefines the same constructor.

You either need to get rid of the constructor definition in the class

Student(int matriculation_number) : Person(name, surname, age){};
//becomes
Student(int matriculation_number);

or get rid of the constructor in the cpp file.

Also name, surname, age, vorname, nachname, alter do not appear anywhere in the code you have provided. This will not compile unless they declared somewhere else.

EDIT:

From the comments it looks like your Student constructor should be

Student(string n, string s, int a, int mn) : Person(n, s, a), matriculation_number(mn) {}

And you can put that in the header and you do not need a constructor definition in the cpp file.

Answer 2

Your error is here:

Student(int matriculation_number) : Person(name, surname, age){};

Remove the {} and the base ctor call:

Student(int matriculation_number);

Answer 3

You already defined the constructor body of student:

Student(int matriculation_number) : Person(name, surname, age){};

That is already a complete implementation of the constructor body, you should write this in the header:

Student(int matriculation_number);