Classes with Other Classes as Member Data

Hi,

I am learning C++ at the moment and I am struggling with the following:

Classes with Other Classes as Member Data.

I am wondering if anyone could show me a quick (commented) example of how this works.


This is from the book I am learning from BTW:

It is not uncommon to build up a complex class by declaring simpler classes and including them in the declaration of the more complicated class. For example, you might declare a wheel class, a motor class, a transmission class, and so forth, and then combine them into a car class. This declares a has-a relationship. A car has a motor, it has wheels, and it has a transmission.

I basically could do with a simpler example so I can get my head around it easier than the example given in the book.


Thanks in advance.

This is a pretty straight-forwards example of thinking in object-oriented programming.

Note: This really just acts like a bunch of structs since none of the objects have any behavior. I also didn't bother with encapsulation; however, it's an integral part which I'm sure you'll learn later.

Code:

---

class Monitor
{
public:
  int size;
  int resWidth;
  int resHeight;
};

class Keyboard
{
public:
  int keys;
};

class Mouse
{
public:
  int buttons;
};

class CPU
{
public:
  double ghzSpeed;
};


// A computer consists of a monitor, keyboard, mouse and cpu.
class DesktopComputer
{
public:
  Monitor monitor;
  Keyboard keyboard;
  Mouse mouse;
  CPU cpu;
};

int main()
{
  DesktopComputer computer;

  // Fill our computer class with information.
  computer.monitor.size = 19;
  computer.monitor.resWidth = 1600;
  computer.monitor.resHeight = 1200;
  computer.keyboard.keys = 109;
  computer.mouse.buttons = 3;
  computer.cpu.ghzSpeed = 3.4;

  return 0;
}

---

Thanks for that! I just took a look over that and now it all makes sense!!

Once again, thanks!