Re: Classes

"Alex Blekhman" <>
Wed, 4 Jun 2008 23:12:47 +0300
First of all, get rid of these pointers. They are completely
redundant. Moreover, your class has a serious bug due to the
erroneous usage of pointers. You forgot to define copy constructor
and assignment operator. So, following code exhibits undefined

    Box b1;
    Box b2;

    // All pointers in b1 instnce are lost,
    // since they are overwritten by values from b2.
    b1 = b2;

} // Oops! Both b1 and b2 attempt to delete the same pointers!

"Fil" wrote:

I am starting with classes and so far I wrote by Box class:

Start of Box.h file.

class Box
float * a;
float * b;
float * c;

Should be:

class Box
    float a;
    float b;
    float c;

Box(float,float, float);
float volume();

End of Box.h file.

Start of Box.cpp file.

#include "Box.h"

Box::Box(float x,float y, float z)
    a = x;
    b = y;
    c = z

Box::Box() : a(1), b(1), c(1)
    // empty body

delete a;
delete b;
delete c;

No need for destructor.

float Box::volume()
    return a * b * c;

End of Box.cpp file.

My first wish is to write this code in a separate cpp file but,
when I tried, the compilation failed. I am not sure what to
write in the main() cpp file to make it work.

No just include Box.h in main.cpp file:

#include "Box.h"

int main()

My second wish is to create a class Boxes with a method add that
would work like a vba collection. My Boxes occurence would be
empty initially. When you call its add method it would add a
Box(1,1,1) to it.

You could use std::vector here:

#include <vector>


typedef std::vector<Box> Boxes;

Boxes boxes;
boxes.push_back(Box(1, 1, 1));
boxes.push_back(Box(10, 20, 30));



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