Re: Tips on Creating Objects

From:
"andrewmcdonagh" <andrewmcdonagh@gmail.com>
Newsgroups:
comp.lang.c++
Date:
11 Feb 2007 10:04:04 -0800
Message-ID:
<1171217043.848104.263910@v45g2000cwv.googlegroups.com>
On Feb 6, 2:55 am, "JoeC" <enki...@yahoo.com> wrote:

I have read books and have ideas on how to create objects. I often
create my own projects and programs. They end up getting pretty
complex and long. I often use objects in my programs they are some of
the most powerful programming tools I have found. Often times as my
program grows so do my objects. Often times I look back and see that
my objects could be broken down int several smaller more re-usable
module pieces of code. Is it a good idea to go back and make several
smaller objects out of a big object.

Here is an example:
class unit{
protected:

  HWND hwnd;
  coord loc;
  coord currentLoc;
  graphics * gr;
  tbox * combatBox;
  std::vector<color>colors;
  std::map<char, coord> keys; //movement engine
  coord n; //directions
  coord s;
  coord e;
  coord w;
  char kind;

  float attack;
  float dattack;
  float defence;
  int move;
  int moved;
  int dmove;
  int range;
  bool canmove;
  bool selected;
  bool mark;
  bool disburse;
  int col;

  void create();
  void displayBox(HDC, coord);
  int convert(const int n){return n * 16;}

public:
  unit();
  unit(HWND,graphics*,int,int,int);
  unit(HWND,graphics*,int,int,int,int,int);
  unit(HWND,graphics*,DWORD,float, float, int, int, int);
  unit(HWND,graphics*,DWORD,float, float, int, int, int, bool);
  unit(unit*);
 ~unit();

  DWORD sideColor(){return colors[0].getCode();}
  int intAttack(){return attack;}
  int intDefence(){return defence;}
  float Attack(){return attack;}
  float Defence(){return defence;}
  int Moved(){return moved;}

  void display(HDC); //display at crrent loc
  void display(HDC, int, int); //display at specific loc
  void display(HDC, int); //display with offset for stacking
  void displayBig(HDC, int, int);
  void change(HWND);
  void update(HWND, coord);

  coord nextCoord(char);
  void mover(coord&, int);
  void reset();
  void tomark(); //marks unit for death;
  bool marked(){return mark;}
  coord getCoord(){return loc;}
  coord getCurrent(){return currentLoc;}
  bool canMove(){return canmove;}
  bool isSelect(){return selected;}
  bool inRange(coord);
  void selectOn(){selected = true;}
  void selectOff(){selected = false;}
  void isArt(){range = 12;}
  void cBoxOn(){combatBox = new tbox;};
  void disbersed();
  void unDisberse(){disburse = false;}
  void write(std::ofstream&);
  void load(std::ifstream&);
  void addk(char k){kind = k;}

};

This is a unit for my game. Basically it is a single game piece.

It does everything I want the unit to do. It has a graphic color it
can fight and move.

It could be graphical.
It could be movable.
It can fight.

I have my has a:

Should I create a graphical that does the graphics
a movable that does the movement and fight-able
because it fights.

Later I could use those simpler types for things in my game that are
graphics but don't move or units that don't fight. I come to this
from experience. I don't want to go back and start editing an object
that works. For my next project I can create these simpler objects
and build more complex ones.


Two of the best design approaches I've used for a number of years now,
is to make my classes conform to the 'Single Responsibility Principle'
and the 'Open Closed Principle'

Google both of these terms and you will find numerous sources of info
on them.

Applying these two design principles leads us to create many small
classes, instead of few large classes and the flexibility of the
design that ensues from it, are hugely beneficial.

HTH

Andrew

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