How to use classes inside headers in c++ - c++

Question

So i'm very new to c++ and i'm trying to test out the simple features it has. I currently have a problem that there is a 'class' type redefinition and I can't figure out why. I have used #pregama once in the header file, but still. I have even tried #ifndef and #define, but they did not work either. I'm using Visual studio 2019 community if that has anything to do with this.
Main.cpp
#include <iostream>
#include "Vectors.h"
using namespace std;
int main() {
double distance = Vector2::Zero().Distance(Vector2(1, 1));
cout << distance;
return 0;
}
Vector2.cpp
#include "Vectors.h"
#include <cmath>
class Vector2 {
public:
double x;
double y;
Vector2(double x, double y) {
this->x = x;
this->y = y;
}
static Vector2 Zero() {
return Vector2(0, 0);
}
static Vector2 One() {
return Vector2(1, 1);
}
double Distance(Vector2 other) {
Vector2 relPos = this->operator-(other);
relPos.x = abs(relPos.x);
relPos.y = abs(relPos.y);
return sqrt(pow(relPos.x, 2) + pow(relPos.y, 2));
}
Vector2 operator + (Vector2 vec) {
return Vector2(x + vec.x, y + vec.y);
}
Vector2 operator - (Vector2 vec) {
return Vector2(x - vec.x, y - vec.y);
}
Vector2 operator * (Vector2 vec) {
return Vector2(x * vec.x, y * vec.y);
}
Vector2 operator / (Vector2 vec) {
return Vector2(x / vec.x, y / vec.y);
}
};
Vectors.h
#pragma once
class Vector2 {
public:
Vector2(double x, double y);
static Vector2 Zero();
static Vector2 One();
double Distance(Vector2 other);
Vector2 operator + (Vector2 vec);
Vector2 operator - (Vector2 vec);
Vector2 operator * (Vector2 vec);
Vector2 operator / (Vector2 vec);
};

Answer 1

You're defining the class once in the header and once in the C++ file. You don't want to do class Vector2 { in the C++ file. Your functions should look like this
Vector2 Vector2::operator+(Vector2 vec) {
return Vector2(x + vec.x, y + vec.y);
}
And should be defined at top-level scope in the C++ file.

Answer 2

First of all, I agree with Silvio Mayolo, You're defining the class once in the header and once in the C++ file. You don't use the keyword class in your cpp file.
And then you need to distinguish between class Vector2 and Vector2(double x, double y); As far as I'm concerned you should try to use Vector2::.
Here is my code:
Vectors.h：
#pragma once
class Vector2 {
public:
double x;
double y;
Vector2(double x, double y);
static Vector2 Zero();
static Vector2 One();
double Distance(Vector2 other);
Vector2 operator + (Vector2 vec);
Vector2 operator - (Vector2 vec);
Vector2 operator * (Vector2 vec);
Vector2 operator / (Vector2 vec);
};
Vector2.cpp：
#include "Vectors.h"
#include <cmath>
double x;
double y;
Vector2::Vector2(double x, double y)
{
this->x = x;
this->y = y;
}
Vector2 Vector2::Zero() {
return Vector2(0, 0);
}
Vector2 Vector2::One() {
return Vector2(1, 1);
}
double Vector2::Distance(Vector2 other) {
Vector2 relPos = this->operator-(other);
relPos.x = abs(relPos.x);
relPos.y = abs(relPos.y);
return sqrt(pow(relPos.x, 2) + pow(relPos.y, 2));
}
Vector2 Vector2::operator + (Vector2 vec) {
return Vector2(x + vec.x, y + vec.y);
}
Vector2 Vector2::operator - (Vector2 vec) {
return Vector2(x - vec.x, y - vec.y);
}
Vector2 Vector2::operator * (Vector2 vec) {
return Vector2(x * vec.x, y * vec.y);
}
Vector2 Vector2::operator / (Vector2 vec) {
return Vector2(x / vec.x, y / vec.y);
}
Main.cpp：
#include <iostream>
#include "Vectors.h"
using namespace std;
int main() {
double distance = Vector2::Zero().Distance(Vector2(1, 1));
cout << distance;
return 0;
}