Refactoring The Prototype - Developing Games With Ruby - page 82

8 if trajectory_length > MAX_DIST
9 object . target_x, object . target_y = point_at_distance( MAX_DIST )
10 end
11 end
12
13 def update
14 fly_speed = Utils . adjust_speed(object . speed)
15 fly_distance = ( Gosu . milliseconds - object . fired_at) * 0.001 *
fly_speed
16 object . x, object . y = point_at_distance(fly_distance)
17 object . explode if arrived?
18 end
19
20 def trajectory_length
21 d_x = object . target_x - x
22 d_y = object . target_y - y
23 Math . sqrt(d_x * d_x + d_y * d_y)
24 end
25
26 def point_at_distance (distance)
27 if distance > trajectory_length
28 return [ object . target_x, object . target_y ]
29 end
30 distance_factor = distance . to_f / trajectory_length
31 p_x = x + (object . target_x - x) * distance_factor
32 p_y = y + (object . target_y - y) * distance_factor
33 [ p_x, p_y ]
34 end
35
36

private

37
38 def arrived?
39 x == object . target_x && y == object . target_y
40 end
41 end

BulletPhysics is where the most of Bullet ended up at. It does all the calculations
and triggers Bullet#explode when ready. When we will be implementing collision
detection, the implementation will go somewhere here.
05-refactor/entities/components/bullet_graphics.rb

1 class BulletGraphics < Component
2 COLOR = Gosu :: Color :: BLACK

3
4 def draw (viewport)