Question

I’m almost 100% sure I have the syntax right in both of these classes, however I’m getting the following errors:

For CShape.cpp – “error C2011: ‘CShape’ : ‘class’ type redefinition”
For CCircle.cpp – “error CS2504: ‘CShape’: base class undefined”

Here is the full code for CShape.cpp

#include <iostream>
using namespace std;

class CShape
{
protected:
    float area;
    virtual void calcArea();
public:
    float getArea()
    {
        return area;
    }
}

And here is the code for CCircle.cpp

#include <iostream>
#include "CShape.cpp"
#define _USE_MATH_DEFINES
#include "math.h"
using namespace std;

class CCircle : public CShape
{
protected:
    int centerX;
    int centerY;
    float radius;
    void calcArea()
    {
        area = M_PI * (radius * radius);
    }
public:
    CCircle(int pCenterX, int pCenterY, float pRadius)
    {
        centerX = pCenterX;
        centerY = pCenterY;
        radius = pRadius;
    }
    float getRadius()
    {
        return radius;
    }
}

As you can see, CShape is the base class that CCircle is suppsoed to inherit from. I’m pretty new to C++, so I could have the file structures wrong (maybe the base is supposed to be in a header file?), if something like that matters.

Answer 1

Never #include .cpp files; that will lead to the kind of redefinition errors you are getting. Instead, declare the class in a header file and #include that one, and define the class methods in a .cpp file.

// CShape.h
class CShape
{
protected:
    float area;
    virtual void calcArea();
public:
    float getArea();
}

.cpp file:

// CShape.cpp
#include "CShape.h"
#include <iostream>
using namespace std;

float CShape::getArea() {
    return area;
}

You should split up CCircle similarly – and CCircle.h should #include CShape.h, and CCircle.cpp should #include CCircle.h.