Building Advanced AI - Developing Games With Ruby - page 200

@closest_powerup = nil
if now - ( @powerup_cache_updated_at ||= 0 ) > POWERUP_CACHE_TIMEOUT
@closest_powerup = nil
@powerup_cache_updated_at = now
end
@closest_powerup ||= find_closest_powerup( * suitable)
end
private
def find_closest_powerup ( * suitable)
if suitable . empty?
suitable = [ FireRatePowerup ,
HealthPowerup ,
RepairPowerup ,
TankSpeedPowerup ]
end
@in_sight . select do | o |
suitable . include?(o . class)
end . sort do | a, b |
x, y = @viewer . x, @viewer . y
d1 = Utils . distance_between(x, y, a . x, a . y)
d2 = Utils . distance_between(x, y, b . x, b . y)
d1 <=> d2
end . first
end
# ...
end
It is very similar to AiVision#closest_tank , and parts should probably be extracted
to keep the code dry, but we will not bother.
Seeking Powerups While Roaming
Roaming is when most picking should happen, because Tank sees no enemies in sight and
needs to prepare for upcoming battles. Let's see how can we implement this behavior while
leveraging the newly made AiVision#closest_powerup :
class TankRoamingState < TankMotionState
# ...
def required_powerups
required = []
health = @object . health . health
if @object . fire_rate_modifier < 2 && health > 50
required << FireRatePowerup