Complex queries through multiple models in rails -

this going kind of long, i'm self taught, , i'm afraid i'm making sort of fundamental error causing me lots of issues - i'm going thorough.

the setup (simplified of course - , had change names if see typo, that's not issue, sorry):

class deviceapi < activerecord::base   belongs_to :devices end  class device < activerecord::base   has_and_belongs_to_many :users   has_many :deviceapis end  class user < activerecord::base   has_many :templates, dependent: :destroy   has_many :designs, through: :templates   has_many :deviceapis, through: :devices   has_and_belongs_to_many :devices end  class template < activerecord::base   belongs_to :user   has_many :designs, dependent: :destroy end  class design < activerecord::base   belongs_to :template end 

the explanation:

my program receives data device - each data entry creates deviceapi entry in database. data used templates , designs. users don't have access devices (except admins), , no 1 accesses deviceapis @ all.

now, want able write queries such as:

class placement < activerecord::base . .   # counts number of api entries associated design   self.campaign.user.devices.deviceapis.count end 

further, admins should able restrict users access devices desired. should indirectly restrict access deviceapis, since accessible through devices anyway (they don't have view pages or anything).

specifically, schema (simplified) shows:

activerecord::schema.define(version: ################)   create_table "deviceapis", force: :cascade |t|     t.string   "api_id"   end    create_table "devices", force: :cascade |t|     t.string   "device_guid"     t.integer  "user_ids"   end    create_table "designs", force: :cascade |t|     t.string   "device_id"   end end 

queries should automatically restricted instances device_guid (device) , api_id (deviceapi) match. should further restricted user_ids (device) matching user_id (the primary key of user). more restricted device_id (design) matching device_id (primary key of device).

scopes , methods can handle queries once them working, can't queries come empty or spit out errors. think i'm needing join tables or something.

how build proper join tables this? or there other, more obvious way i'm not seeing? i've spent long time on this, , i'm learning lot in trial fire, not making progress on specific issue - , think it's crippling me in other places.

thanks help!

here think issue.

if log this: placement.campaign.user.devices results. ( don't know relation in placement , campaign guessing.

in console this: ( based on above assumptions ) placement.campaign.user.devices.class should : device::activerecord_associations_collectionproxy or similar.

you not able placement.campaign.user.devices.deviceapi rails don't know 1 of record need deviceapi.

if placement.campaign.user.devices.first.deviceapi should result if placement.campaign.user.devices.first.deviceapi.class should deviceapi or similar.

to query number of deviceapi use join condition.

something user.joins(devices: (:deviceapis) ).where('users.id = ?', current_user.id).count

i assumed have current_user available or put other condition think fits.

please let me know if helps.