trying to link two cpp files with a header - class

Question

I'm trying to call a function from a cpp file (with a list of functions) in another cpp file, I'm using a header file to set the function prototype in both cpp files, my problem is that I'm getting this LNK2019 error. I don't know what i'm doing wrong. I've been going back and forth between a few variations, the current one seems to be the most correct based on what i've read. I've been working on this for hours, reading a bunch of threads, but nothing seems to explain this problem, i'm using microsoft visual studio 2012
this is the header file, Rectangle.h
#pragma once
class Rectangle
{
private:
int width, height;
double gravWidth, gravHeight;
public:
Rectangle();
double getAreaBig();
double getAreaSmall();
int getPerimeter();
void getLength(int b);
void getWidth(int a);
int setLength();
int setWidth();
~Rectangle();
};
this is the cpp file containing the functions, Rectangle.cpp
#include <iostream>
#include "Rectangle.h"
using namespace std;
Rectangle::Rectangle()
{
width = 1;
height = 1;
gravWidth = .5;
gravHeight = .5;
}
double Rectangle::getAreaBig ()
{
return double ((width * height) - (gravWidth * gravHeight));
}
double Rectangle::getAreaSmall()
{
return ((gravWidth) * ( gravHeight));
}
int Rectangle::getPerimeter()
{
return (2 * (width + height));
}
void Rectangle::getLength(int b)
{
height = b;
gravWidth = (1/2 * width);
}
void Rectangle::getWidth(int a)
{
width = a;
gravHeight = (1/2 * height);
}
int Rectangle::setLength()
{
return height;
}
int Rectangle::setWidth()
{
return width;
}
what follows is the app.cpp file, this is where i'm getting the errors, italics are where the errors seem to be pointing too
#include <iostream>
#include "Rectangle.h"
#include <fstream>
#include <iomanip>
#include <cstdlib>
#include <cmath>
#include <string>
#include <sstream>
#include <cstddef>
using namespace std;
int main ()
{
int const WIDTH = 10;
setprecision(2);
int length = 0;
int width = 0;
cin >> width;
cin >> length;
Rectangle garden;
Rectangle gravel;
garden.getLength(length);
garden.getWidth(width);
cout << "Length of lawn: " << garden.setLength() << "Width of lawn: " << garden.setWidth();
cout << "Cost of grass: " << garden.getAreaBig();
cout << "Length of gravel: ";
cout << "Width of gravel: ";
cout << "Cost of gavel: ";
system ("pause");
}

Answer 1

The first thing that I see is that you are not instantiating the rectangles.

Answer 2

What about defining
~Rectangle();
somewhere? If your destructor is not going to do anything, you can just provide an empty body in the header file.
~Rectangle() {};
(And just in case, make it virtual, it's always a good habit.)