Making The Prototype Playable - Developing Games With Ruby - page 152

Damage tracks it's instances and starts removing old ones when MAX_INSTANCES are
reached. Without this optimization, the game would get increasingly slower every time
somebody shoots.

We have also added a new game object trait - effect? returns true on Damage and
Explosion , false on Tank , Tree , Box and Bullet . That way we can filter out effects
when querying ObjectPool#nearby for collisions or enemies.
09-polishing/entities/object_pool.rb

1 class ObjectPool
2

attr_accessor :objects , :map , :camera

3
4 def initialize
5 @objects = []
6 end
7
8 def nearby (object, max_distance)
9

non_effects . select do | obj |

obj != object && 10

(obj . x - object . x) . abs < max_distance && 11

(obj . y - object . y) . abs < max_distance &&

12

Utils . distance_between( 13

obj . x, obj . y, object . x, object . y) < max_distance

14

15 end
16 end
17
18 def non_effects
19 @objects . reject( & :effect? )
20 end
21 end

When it comes to rendering graphics, to make an impression of randomness, we will cycle
through several different damage images and draw them rotated:
09-polishing/entities/components/damage_graphics.rb

1 class DamageGraphics < Component
2 def initialize (object_pool)
3 super
4 @image = images . sample
5 @angle = rand ( 0. . 360 )
6 end
7
8 def draw (viewport)