Thread: C++ problem with Shape hierarchy ~

Originally Posted by laserlight

When we say "compile", we mean "compile without errors". Your code in post #14 should not compile, i.e., the compiler should be reporting at least one error.

what do you think is wrong with the program and how can i fix it?

What's wrong is that the main() you provided won't compile, so there's no way to diagnose your problem until you post the real one. I know you think it's compiling, but it's not valid C++.

Maybe it's not added to your VC++ project and you think it is? Export a makefile and post that, maybe.

Originally Posted by medievalelks

What's wrong is that the main() you provided won't compile, so there's no way to diagnose your problem until you post the real one. I know you think it's compiling, but it's not valid C++.

Maybe it's not added to your VC++ project and you think it is? Export a makefile and post that, maybe.

what i want to know is how do i run a program with function like Shape* getShape()??? That's what i really want to know.

Originally Posted by laserlight

You would do something like this:

Code:

#include <iostream>

// other includes etc
// ...

int main()
{
    Shape* shape = getShape();
    std::cout << shape->toString() << std::endl;
    delete shape;
}

It doesnt work. It says that getShape(); is unidentified.

Originally Posted by laserlight

That means that you did not modify my example correctly.

Okay, I think we need to do some serious hand holding here. Ditch your code and try this:

Code:

#include <iostream>

class Shape
{
public:
    virtual ~Shape() {}
    virtual unsigned int area() const = 0;
};

class Square : public Shape
{
public:
    explicit Square(unsigned int length) : length(length) {}

    virtual unsigned int area() const
    {
        return length * length;
    }
private:
    unsigned int length;
};

class Rectangle : public Shape
{
public:
    Rectangle(unsigned int length, unsigned int width)
        : length(length), width(width) {}

    virtual unsigned int area() const
    {
        return length * width;
    }
private:
    unsigned int length;
    unsigned int width;
};

Shape* getShape()
{
    /* Okay, let's play a game: if the user enters an odd number, we create
     * a square of side 5. Otherwise, we create a 11 by 7 rectangle.
     */
    std::cout << "Please enter an integer: ";
    int num;
    std::cin >> num;
    if (num % 2 == 0)
    {
        return new Rectangle(11, 7);
    }
    else
    {
        return new Square(5);
    }
}

int main()
{
    Shape* shape = getShape();
    std::cout << shape->area() << std::endl;
    delete shape;
}

That's the thing, the getShapte() function is suppose to get the dimensions from the input stream, then store them in an array. The getShape function is supposed to be in getShape.cpp. Then the main function is suppose to be a different source file with only the Shape.h as #include header while the getShape is supposed to have the circle.h, rectangle.h and square.h as headers.

It still doesn't work
here is what i wrote. I wrote again.

Code:

#include "Circle.h"
#include "Square.h"
#include "Rectangle.h"



using std::string;
using namespace std;

Shape* getShape()
{

do {

string color;
double length, width, rad, side;
string shapetype;
Shape *myshape;



cout << "Enter the shape's color (or 'done')..." << endl;
cin >> color;
cout << "Enter shape type..." << endl;
cin >> shapetype;
if (shapetype == "done")
{
return NULL;
}
if (shapetype == "circle")
{
cout << "Enter the radius..." << endl;
cin >> rad;
myshape = new circle (color, rad);
return myshape;
}


if (shapetype == "square")
{
cout << "Enter the side length..." << endl;
cin >> side;
myshape = new square (color, side);
return myshape;
}

if (shapetype == "rectangle")
{
cout << "Enter the length..." << endl;
cin >> length;
cout << "Enter the width..." << endl;
cin >> width;
myshape = new rectangle (color, width, length);
return myshape;
}
else{
cout << "Invalid input. Please enter \"circle\", \"square\", \"rectangle\" or \"done\"" << endl;
continue;
}


}while (true);

}

It still doesn't show anything when i run main.

Where's main?

why is it that the compiler can't recognize the getShape() function.

Originally Posted by laserlight

Where does the compiler not recognise it?

Let's check: are you able to compile the source files for Circle, Square and Rectangle? Are you are to compile the source file that contains the definition (i.e., implementation) of getShape()?

the source file shouldn't contain the implementation of getShape(). getshape is supposed to be the source file getShape.cpp and include the headers of circle.h, rectangle.h and square.h. Main.cpp is supposed to be a different source file and include only shape.h header.

I've already test the source codes i wrote for circle, rectangle and square. .The problem is with getShape() because i can't call it in main.