Re: Inheritance

"Tom Serface" <>
Fri, 30 Mar 2007 07:39:38 -0700
Keep going Al. You'll get it. Be sure to continue asking questions too.
It's one of those things that just kind of clicks. Note, in your case a
"Division" is not a kind of "League" or "Session". Those are all different
things or perhaps collections of things. For example a Division is a
collection of Teams, but a Division is not a kind of Team.

However, a "First base player" is a kind of player that does different
things than a "Right fielder". So both of these types could be derived from
a "Player". For example:

CPlayer - base class for player information

CFirstBase : public CPlayer
COutfieder : public CPlayer
CRightField : public COutfield

Even though this is technically true, I think in your case making it less
complicated would server you better. For example, a CPlayer class could
simply contain a member:


PlayingPosition m_nPosition;

That could be assigned for each player. Then you could havea collection:

// The CTeam contains CPlayers objects, and CManager objects
class CTeam : public CObArray
    // Construction/Destruction
    // Attributes

    // Operations

// Implementation

#define NUM_GAMES 10

// The CDivision contains CTeam objects
class CDivision: public CObArray
    // Construction/Destruction
    // Attributes

    // Operations

// Implementation
        CString GetTeamname() {return m_csTeamname;};
        void SetTeamname(CString csTeamname) {m_csTeamname = csTeamname;};
        CString GetTeammascot() {return m_csTeammascot;};
        void SetTeammascot(CString csTeammascot) {m_csTeammascot =
        CString GetManager() {return m_csManager;};
        void SetManager(CString csManager) {m_csManager = csManager;};
        CString GetAsstManager() {return m_csAsstManager;};
        void SetAsstManager(CString csAsstManager) {m_csAsstManager =
        UINT GetStanding() {return m_csStanding;};
        void SetStanding(UINT nNewStanding) {m_nStanding = nNewStanding;};
        WINORLOSE GetWinsLosses(nGame) {
                if(nGame > 0 && nGame < NUM_GAMES)
                     return m_nWinsLosses[nGame];
                    return GAME_UNKNOWN;
        void SetWinLossForGame(UINT nGame, WINORLOSE nWinOrLose) {
                if(nGame > 0 && nGame < NUM_GAMES)
                     m_nWinsLosses[nGame] = nWinOrLose;

        int FindTeam(LPCTSTR TeamName); // Get the index for a particular
team given their team name by looping through list
return -1 if team not in list
        AddTeam(/*... info about team*/);
        DeleteTeam(LPCTSTR TeamName);
        // whatever

        CString m_csTeamname;
        CString m_csTeammascot;
        CString m_csManager;
        CString m_csAsstManager;
        UINT m_nStanding;
        WINORLOSE m_nWinsLosses[NUM_GAMES];

Let's say you had a "Division" list that had several team lists.

CDivision m_Division;

  int nTeams = m_nDivision->GetSize();

  // Loop through all teams
  for(int i = 0; i < nTeams;; ++i) {
       CTeam *pInfo = (CTeam *)m_Division->GetAt(i);
       if(pInfo) {
          CString csTeamname = pInfo->GetTeamname();
          CString csTeammascot = pInfo->GetTeammascot();
            // ... do whatever you want with it.

You could also extend it to collect Divisions into Leagues or as far out as
you want to go. I'm not sure about the sport so I just picked an example.
Hope this helps some. Keep asking questions.


"Al" <> wrote in message

Yes I think you are right, it is a bad design. I have changed the design
so that,
class a:public CObject
class b:public CObject
class c: public b
a = League
b = Session
c = Division
I had this all screwed up because I was trying to have multi arrays of
different classes. Now I have separated League from Session, derived
from Session and will save Division in a CTypedPtrArray.
I have not gotten around to it yet because I am redoing alot of my
application because of some posts that I have read about a proper design.
think that the way that I am going to use the previous classes and the way
that I am going to save them will work. If you see something that does not
look right please let me know.
Just Al

"Joseph M. Newcomer" wrote:

Only if the pilot is rated for aerobatics...

(Couldn't resist...)

Yes, that's another case. It gets trickier, and inheritance breaks down
after a while.

class WheeledVehicle {
int wheels;

class Unicycle : public WheeledVehicle
Unicycle() : wheels(1) { }

class WingedVehicle {
             int wings;
             int engines;

class biplane: public WheeledVehicle, WingedVehicle {
         biplane () : wings(4), wheels(3)

class monoplane : public WheeledVehicle, WingedVehicle {
        monoplane() : wings(2) {}

class glider : public monoplane {
       glider () : engines(0), wheels(2) {}

class Bomber : public monoplane {
      int BombLoad;

class PoweredPlane {
     int engines;
     typedef { Piston, Jet } EngineType;
     EngineType type;

class PropPlane {
       int bladesperprop;

class Jet : public PoweredPlane {
        Jet() : type(Jet);

class B52 : public monoplane, bomber, Jet {
       B52() : engines(8), wheels(8), BombLoad(CLASSIFIED_VALUE) {}

class C130 : public monoplane, Jet, PropPlane {
       C130: engines(4), wheels(8), bladesperprop(4) {}

Given this hierarchy, I can probably come up with actual planes that
don't fit it. And on
the whole, you can't do it without multiple inheritance. What about a
jet-propelled race
car, or even a jet-propelled bicycle? What about model airplanes powered
by rubber bands?
We used to go through exercises like this back when we were designing
languages, and it became a weekly exercise to describe vehicles. For
example, how do you
describe an airplane with skis or pontoons instead of wheels? Oh, forgot
about that. So
a new hierarchy comes around. What about bulldozers or tanks with treads
instead of
wheels? A halftrack? A snowmobile? This was in the days before the
Internet and Google,
and we would spend hours in the library looking for photos of odd
vehicles that our
current hierarchy couldn't describe, and try to work out a new hierarchy
that could
describe all vehicles (hot air balloons, dirigibles, hang gliders, kites,
roller skates,
skateboards,helicopters, autogyros,! It's been thirty years, and
what I remember
was that we couldn't get a decent solution. The really bad thing was
that we couldn't
somehow attach attributes, but our whole hierarchy would disintegrate.
The folks in AI
developed entirely different mechanisms for describing objects, that were

So hierachical systems will give superficially simple solutions to
trivial problems, but
they dont' give solutions to all representations.

Note that I stopped at weeks in my description, because months get
trickier, and what's a
year? 365, 366, or 365.25?

Key here is that anything in class A should only reference classes that
are not related,
or its superclasses, but not its subclasses. Once you start building
dependencies, life gets fairly miserable. And you can't do anything that
requires that
the superclass have instances of the subclass, although it could have
pointers to a
subclass, but at this point you're into really weird, and probably very
bad, design.

On Wed, 28 Mar 2007 09:44:07 -0700, Al <>

Would the post before this one with airplane as a class inverted also?

Joseph M. Newcomer [MVP]
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