error LNK2018: unresolved external symbol (referring to constructors)

[SuperLauraRae]

This is the first time I have used classes in C++. This program is fairly simple, I am to create a Student class with 4 instance variables. Then create a default and non-default constructor as well as a member function to display the instance variables. In the main body of my program I declare two objects using the two different constructors, then call the member function in order to display the data. There is something wrong, and as I am a beginner I cannot figure it out for the life of me. I receive two LNK2019: unresolved external symbol errors that are referring to both of my constructors being referenced in my main function. Any help would be greatly appreciated.

Student.h file

// class for college student
class Student
{

public:

	// instance/member variables
	std::string studentName;
	int phoneNumber;
	int studentNumber;
	double currentGPA;

	// member function to display instance variables
	void displayValues();

public:
	
	// default constructor that assigns deault values to instance variables
	Student() : studentName ("Laura"), phoneNumber (6514923845), studentNumber (0002), currentGPA (3.8) {}
	
	// non default constructor that takes 4 variables as parameters and sets to instance variables
	Student(std::string studentName, int phoneNumber, int studentNumber, double currentGPA);
	
	// default deconstrucor
	~Student();
};

Student.cpp file

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

using namespace std;

// main function
int main()
{

	// declare default object
	Student student_one;

	// declare non default object
	Student student_two("Numen", 9523937467, 0002, 3.5);

	// call displayValue()
	student_one.Student::displayValues();

	// again call displayValue()
	student_two.Student::displayValues();

}

// member function to display instance variables
void Student::displayValues()
{
	cout << studentName << endl;
	cout << phoneNumber << endl;
	cout << studentNumber << endl;
	cout << currentGPA << endl;
}

[shadowCODE]

LNK2018: unresolved external symbol often means you are calling a function that has not been defined.

non-default constructor declaration at line 22 of student.h, does not have any definition.

[rjvc]

// non default constructor that takes 4 variables as parameters and sets to instance variables
Student(std::string studentName, int phoneNumber, int studentNumber, double currentGPA);

No implementation here. You could try adding {} but that would be weird, since you'll most likely want to take some operations here.

~Student();

here too. You can actually get rid of this if you wont do anything before the object(in this case the class) destroys.

Hope this helps.

[TheIdeasMan]

Hi,

It might help a little, if I mention to name the header & .cpp files the same as the class. That is Student.h and Student.cpp. Student.cpp has the implementation code for the class functions. Name the file with main in it something else.

:+)

[rjvc]

^The man was right...hahaha..I didnt even take a good look at your filenames.. -_-

[SuperLauraRae]

Got it! Thank you much!