gistfile1.txt

«Basic class for game objects
  Provides:
    − Basic fields for position and motion
    − Tracking of what game objects exist in the game
    − Initialize method
    − draw and tick generic procedures

   To customize:
   − Make sure your game calls [initialize-game-objects] when it starts
   − Create a new subclass of GameObject
   − Add an initialize method, if needed
      Remember to use [call-next-method], if you do.
   − Add methods for draw and tick
»

[define all-game-objects “List of all objects currently in play”
[new ArrayList]]

[define initialize-game-objects
[→ [all-game-objects.Clear]]]

[define for-all-game-objects
[proc →
[for-each proc all-game-objects]]]

[define all-solid-game-objects “List of all solid objects currently in play.”
[filter [n → [= true n.solid]] all-game-objects]]

[define GameObject “Base class of all game objects”
[class [GameObject]
Object
position orientation
velocity angular-velocity
delete?]]

[define tick “Lets an object update itself as it sees fit.”
[generic-procedure]]
[define draw “Draws a game object using the specified Graphics object”
[generic-procedure]]

[define-method [initialize [GameObject o]]
[o.delete? ← false]
[all-game-objects.Add o]
[if [null? o.position]
[o.position ← [point 0 0]]]
[if [null? o.orientation]
[o.orientation ← 0.0]]
[if [null? o.velocity]
[o.velocity ← [point 0 0]]]
[if [null? o.angular-velocity]
[o.angular-velocity ← 0]]]

[define destroy “Remove game-object from the game's list of active objects”
[game-object →
[game-object.delete? ← true]]]