Rails deep nested associations

deep.sh

➜ bin/rails c
Loading development environment (Rails 5.2.3)
2.6.2 :001 > class Profile < ApplicationRecord
2.6.2 :002?>     has_many :persons, inverse_of: :profile, dependent: :destroy
2.6.2 :003?>     has_many :foos, :through => :persons
2.6.2 :005?>     accepts_nested_attributes_for :persons
2.6.2 :006?>   end
 => [:persons]
2.6.2 :007 > class Person < ApplicationRecord
2.6.2 :008?>     has_one :foo, inverse_of: :person, dependent: :destroy
2.6.2 :009?>     has_one :bar, :through => :foo
2.6.2 :011?>      belongs_to :profile, inverse_of: :persons
2.6.2 :012?>     belongs_to :person_type
2.6.2 :014?>     accepts_nested_attributes_for :foo
2.6.2 :015?>   end
 => [:foo]
2.6.2 :016 > class Foo < ApplicationRecord
2.6.2 :017?>     has_one :bar, inverse_of: :foo
2.6.2 :018?>   belongs_to :person # you are missing this
2.6.2 :019?>   end
 => {"bar"=>#<ActiveRecord::Reflection::HasOneReflection:0x00007f9ae02a9090 ...}

2.6.2 :020 > class Bar < ApplicationRecord
2.6.2 :021?>   belongs_to :foo, inverse_of: :bar
2.6.2 :022?>   end
 => {"foo"=>#<ActiveRecord::Reflection::BelongsToReflection:0x00007f9ae02fb5c0 ...}

2.6.2 :023 > profile = Profile.new
 => #<Profile id: nil>
2.6.2 :024 > person = profile.persons.build
 => #<Person id: nil, profile_id: nil>
2.6.2 :025 > foo = person.build_foo
 => #<Foo id: nil, person_id: nil>
2.6.2 :026 > foo.build_bar
 => #<Bar id: nil, foo_id: nil>
2.6.2 :028 > profile.persons[0].foo.bar
 => #<Bar id: nil, foo_id: nil>
2.6.2 :030 > profile.save
   (0.3ms)  BEGIN
  Profile Create (1.1ms)  INSERT INTO "profiles" DEFAULT VALUES RETURNING "id"
  Person Create (0.7ms)  INSERT INTO "people" ("profile_id") VALUES ($1) RETURNING "id"  [["profile_id", 2]]
  Foo Create (0.5ms)  INSERT INTO "foos" ("person_id") VALUES ($1) RETURNING "id"  [["person_id", 2]]
  Bar Create (0.7ms)  INSERT INTO "bars" ("foo_id") VALUES ($1) RETURNING "id"  [["foo_id", 2]]
   (5.6ms)  COMMIT
 => true

tables.sql

CREATE TABLE public.profiles (
	id int4 NOT NULL GENERATED BY DEFAULT AS IDENTITY,
	CONSTRAINT profiles_pk PRIMARY KEY (id)
);

CREATE TABLE public.people (
	id int4 NOT NULL GENERATED BY DEFAULT AS IDENTITY,
	profile_id int4 NOT NULL,
	CONSTRAINT people_pk PRIMARY KEY (id)
);

CREATE TABLE public.foos (
	id int4 NOT NULL GENERATED BY DEFAULT AS IDENTITY,
	person_id int4 NOT NULL,
	CONSTRAINT foos_pk PRIMARY KEY (id)
);

CREATE TABLE public.bars (
	id int4 NOT NULL GENERATED BY DEFAULT AS IDENTITY,
	foo_id int4 NOT NULL,
	CONSTRAINT bars_pk PRIMARY KEY (id)
);