I've been trying hard to solve this problem but i really don't know what is happening. I have this small piece of code :

DiscoveredLocation.find_by_user_id(user.id, :include => [:boss_kills])

The models are :

DiscoveredLocation(id, user_id, boss_location_id)
BossKill(user_id, monster_id)

and associations :

Monster belongs_to :boss_location
Monster has_many :boss_kills

BossKill belongs_to :user
BossKill belongs_to :monster


DiscoveredLocation belongs_to :user
DiscoveredLocation  belongs_to :boss_location

DiscoveredLocation  has_many :monsters, :through => :boss_location

DiscoveredLocation  has_many :boss_kills, :through => :monsters

When i executed the find_by i get this error :

NoMethodError in BossesController#index

You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.each

If i change the include option to any other model, like :monster, it works great. I'm pretty much owned by this problem :P. Maybe somebody can help me ? :)