ruby - Rails 4 association connection -

i'm trying figure out association between 3 models have.

challenge, sip, user

user can create sip, , users can submit challenges sip; sips has many challenges

challenge.rb

class challenge < activerecord::base   belongs_to :user   belongs_to :sip, counter_cache: true end 

sip.rb

class sip < activerecord::base   belongs_to :user   has_many :challenges end 

user.rb

class user < activerecord::base   has_many :challenges   has_many :sips end 

here columns:

challenge: id, user_id, sip_id sip: id, user_id user: id 

in in sip view, i'm trying list of users this:

- @sip.each |sip|   = sip.challenges.users.to_json 

ultimately, want users have submitted challenges belongs sip.

sip.challenges collection, have map on users. that's going collection of collections of users, flatten it, , uniq it, , compact remove nils:

sip.challenges.map(&:user).flatten.uniq.compact

flatten turns [[1,2], [2,3]] [1,2,2,3], uniq turns [1,2,3].

map(&:user) sends user each item in enumerable (collection) that's left of map, in case, each challenge in challenges.

is efficient? uh... left exercise you.

edit: add html tags: result of doing enumerable, can each on it:

%ul   - sip.challenges.map(&:user).flatten.uniq.compact.each |user|     %li= user