"error LNK2019: unresolved external symbol "public: __thiscall : constructor" concern [duplicate] - c++

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What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 7 years ago.
I am currently trying to create a simple implementation of a Module class and a Student class in c++. These classes will incorporate specific modules and the individual students enrolled in them. However, I can't seem to get round this particular error message whenever I try to make a Module or Student object.
It will probably be something simple I missed but I have uploaded my header and source files below. Please help, this is driving me crazy. Thanks in advance.
student.h:
#include "stdafx.h"
#include <string>
class Student {
public:
Student(std::string, std::string, int);
std::string getName() const { return name; }
std::string getDegree() const { return degree; }
int getLevel() const { return level; }
private:
std::string name;
std::string degree;
int level;
};
module.cpp:
// student.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include "module.h"
#include <vector>
#include <iostream>
#include <string>
using namespace std;
void Module::enrol_student(Student studentY) {
students.push_back(studentY);
}
void Module::attendance_register() {
string nameX;
cout << "Attendance Register:\n" << endl;
for (int i = 0; i < students.size(); i++) {
Student studentX = students.at(i);
nameX = studentX.getName();
cout << nameX << endl;
}
}
module.h:
#include "stdafx.h"
#include "student.h"
#include <string>
#include <vector>
class Module {
public:
Module(std::string, std::string, std::vector<Student>);
std::string getModCode() { return modCode; }
std::string getModTitle() { return modTitle; }
void attendance_register();
void enrol_student(Student);
private:
std::string modCode;
std::string modTitle;
std::vector<Student> students;
};
testCode.cpp
// testCode.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
int _tmain(int argc, _TCHAR* argv[])
{
return 0;
}
#include "module.h"
#include <vector>
#include <iostream>
#include <string>
using namespace std;
int main() {
//Initial Test Data
Student student1("Arthur Smith", "Computer Science", 1);
return 0;
}

Answer 1

You need to define the constructors you declared in your classes. In student.cpp you need something like this:
Student::Student(std::string name, std::string degree, int level) : name(name), degree(degree), level(level)
{
}
This will initialise the members with the values provided.
And similar for Module.