Thread: Classes with Other Classes as Member Data

  1. #1
    Registered User
    Join Date
    Sep 2005

    Classes with Other Classes as Member Data


    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.
    Last edited by njd; 09-27-2005 at 09:10 AM.

  2. #2
    Registered User
    Join Date
    Jan 2003
    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.
    class Monitor
      int size;
      int resWidth;
      int resHeight;
    class Keyboard
      int keys;
    class Mouse
      int buttons;
    class CPU
      double ghzSpeed;
    // A computer consists of a monitor, keyboard, mouse and cpu.
    class DesktopComputer
      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;
    Last edited by Speedy5; 09-27-2005 at 09:32 AM.

  3. #3
    Registered User
    Join Date
    Sep 2005
    Thanks for that! I just took a look over that and now it all makes sense!!

    Once again, thanks!

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