ruby on rails 4 - Can't get has_many & belongs_to in same model to work -

it has been while since asked around here. since have started playing around ruby, , can't head around this, decided come here guidance.

i've read quite few examples now, don't find proper path walk solve problem.

the idea following :

you have :

• a family
• a person

their relationship following :

• there 1 person 'head' of family
• every person part of family (be multiple persons or himself in it)

now current validation makes impossible perform this, idea there no such thing family without head, , no person without family. i've tried express following way :

family class

class family < activerecord::base    validates :head_id, presence: true    belongs_to :head, :class_name => person, foreign_key: 'head_id'   has_many :persons end 

person class

class person < activerecord::base    validates :family_id, presence: true   validates :first_name, presence: true    belongs_to :family end 

would soul kind offer me advice?

the migration has family_id on person-class side, family consists of column being person_id.

family migration

class createfamilies < activerecord::migration   def change     create_table :families |t|       t.integer :head_id        t.timestamps null: false     end   end end 

person migration

class createpersons < activerecord::migration   def change     create_table :persons |t|       t.string :first_name       t.string :last_name       t.integer :age       t.integer :family_id        t.timestamps null: false     end   end end 

you got circular dependency here. cannot create families nor people. circular dependency indicates there's third element missing. more eloquently , not related .

there 2 kind of membership, head , non-head. once make them obvious in code circular dependency solved.

there few solutions need find 1 fits best. mine.

create membership join table

class family   validates :memberships, presence: true, on: :update   has_many :memberships   has_many :people, through: :membership    after_create :create_head_membership    private    def create_head_membership     memberships.create role: 'head' # filled later   end end  class membership   belongs_to :family   belongs_to :person end  class person   has_many :memberships   has_one :family, through: :membership # has_many, amrite?   validates :memberships, presence: true, on: :update end 

the important thing avoid person/family direct manipulation, rather create handle process , wrap in transaction

class god   def make_family head_attrs     fam, head = nil     family.transaction       fam = family.create!       head = person.create! head_attrs       fam.memberships.first.update_attribute! :person_id, head.id     end      fam   end end