Data and Classes

[Sionofdarkness]

I know what data is, I mean outside of programming languages, but I read that data and methods make classes. I now know what methods are, but what is "data". Is it just everything else, like the syntax and such?

[WingedPanther]

the "data" would be the variables within the class. It could be ints, floats, or even other classes.

[Sionofdarkness]

There can be classes within a class? Would that make it a "sub-class" (I've never heard the term but I assume that would be what they're called).

[WingedPanther]

A subclass usually refers to a class that has been derived from another class. For example, the class of dogs is a subclass of the class of animals. (This terminology might come from set theory). A class within a class might be called a member class.

As far as can it be done, yes. Consider your car: it has an engine, wheels, etc. So if you are modeling it with classes, you would have an engine class, a wheel class, and a car class that has an engine and an array of wheels as members. The engine would have information such as the number of cylinders. The wheels would have information such as size and if they're flat or spare. The car would include the manufacturer.

[Sionofdarkness]

Your examples, as always, are very helpful. Can you give an example using a real piece of code as well?

[WingedPanther]

I'm a little rusty on Java, so my example will be in C++.

class piece
{
  public:
    bool moveTo(x,y);
    bool isThreatend();
    TYPE pieceType();
  private:
    COLOR color;
}

class pawn : piece
{
  private:
    bool EnPassante;
}

pawn myPawn;
piece myPiece;

myPiece has one data values: myPiece.color
myPawn has two data value: myPawn.color (inherited from the piece class) and myPawn.EnPassante
COLOR is an enumeration for the colors of chess pieces (Black and White).

Now I can make another class:

class Board
{
  public:
    void PlayGame();
  private:
    piece pieces[16][2];
}

This class has 32 pieces as data, each having a color and the ability to move.

Now, with a few more classes and some code for the methods, you have a chess program