Refactoring The Prototype - Developing Games With Ruby - page 81

Since explosion sounds are triggered only once, when it starts to explode,

ExplosionSounds is a static class with play method.

Refactoring Bullet

Now, let's go up a little and reimplement our Bullet :
05-refactor/entities/bullet.rb

1 class Bullet < GameObject
2 attr_accessor :x , :y , :target_x , :target_y , :speed , :fired_at

3
4 def initialize (object_pool, source_x, source_y, target_x, target_y)
5 super (object_pool)
6 @x , @y = source_x, source_y
7 @target_x , @target_y = target_x, target_y
8 BulletPhysics . new( self )
9 BulletGraphics . new( self )
10 BulletSounds . play
11 end
12
13 def explode
14 Explosion . new(object_pool, @x , @y )
15 mark_for_removal
16 end
17
18 def fire (speed)
19 @speed = speed
20 @fired_at = Gosu . milliseconds
21 end
22 end

All physics, graphics and sounds are extracted into individual components, and instead
of managing Explosion , it just registers a new Explosion with ObjectPool and
marks itself for removal in explode method.
05-refactor/entities/components/bullet_physics.rb

1 class BulletPhysics < Component
2

START_DIST = 20

MAX_DIST = 300 3

4
5 def initialize (game_object)
6 super
7

object . x, object . y = point_at_distance( START_DIST )