value being changed to random number on function call? - c++

Question

#include <iostream>
#include "Shapes.h"
int main()
{
//variables
int height = 0;
int width = 0;
Rectangle rect = Rectangle();
Triangle tran = Triangle();
Square sqar = Square();
std::cout << "What is the width of the shape? ";
std::cin >> width;
std::cout << "What is the height of the shape?";
std::cin >> height;
rect.set_lengths(width, height);
std::cout << "If the shape is a triangle, the area is " << tran.area() << "." << std::endl;
std::cout << "If the shape is a rectangle, the area is " << rect.area() << "." << std::endl;
std::cout << "If the shape is a square, the area is " << sqar.areaByWidth() << " by the width value," << std::endl;
std::cout << "and " << sqar.areaByHeight() << " by the height value." << std::endl;
system("pause");
}
Header file:
//Our base class
class Shape
{
protected:
int width, height, shapes = 0;
public:
void set_lengths(int width, int height)
{
width = width; height = height;
}
};
//Rectangle is a shape
class Rectangle : public Shape
{
public:
Rectangle()
{
std::cout << "Created a rectangle!\n";
shapes = shapes + 1;
}
~Rectangle()
{
shapes = shapes - 1;
}
int area()
{
return width * height;
}
};
//Triangle is a shape
class Triangle : public Shape
{
public:
Triangle()
{
shapes = shapes + 1;
std::cout << "Created a triangle!\n";
}
~Triangle()
{
shapes = shapes - 1;
}
int area()
{
return width * height / 2;
}
};
//Square is a shape
class Square : public Shape
{
public:
Square()
{
shapes = shapes + 1;
std::cout << "Created a square!";
}
~Square()
{
shapes = shapes - 1;
}
int areaByWidth()
{
return width * width;
}
int areaByHeight()
{
return height * height;
}
};
When I set the values, it works fine (shows the correct value in visual studio debugger), but when I call area() it brings back -846388729 or something similiar? Why is the value being reset? I have been banging my head against a wall for hours on this. Seems like a common problem to noobies like myself but I'm not understanding the other solutions on here :(

Answer 1

The function set_lengths did not set the member variable correctly, just set the value back to the function arguments.
change
void set_lengths(int width, int height)
{
width = width; height = height;
}
to
void set_lengths(int width, int height)
{
this->width = width; this->height = height;
}
Or change the name of the member variables for a good habit:
int width_, height_, shapes_;
void set_lengths(int width, int height)
{
width_ = width;
height_ = height;
}

Answer 2

Becuase width and height are not initilized.
Change the line to:
int i = 0, j = 0, k = 0;
Also, you're only setting the dimension of the rect object, not the triangle or the square.