Add associations

app/models/membership_app.rb

@@ -4,6 +4,8 @@ class MembershipApp < ApplicationRecord
   belongs_to :account, inverse_of: :own_membership_apps
   belongs_to :country_state, optional: true
 
+  has_one :regional_office, through: :country_state
+
   validates :email, presence: true, format: Devise.email_regexp
 
   validates :first_name, presence: true

app/models/regional_office.rb

@@ -3,5 +3,7 @@
 class RegionalOffice < ApplicationRecord
   belongs_to :country_state
 
+  has_many :membership_apps, through: :country_state
+
   validates :country_state_id, uniqueness: true
 end

spec/models/membership_app_spec.rb

@@ -8,6 +8,8 @@ RSpec.describe MembershipApp do
   it { is_expected.to belong_to(:account).inverse_of(:own_membership_apps) }
   it { is_expected.to belong_to(:country_state).optional }
 
+  it { is_expected.to have_one(:regional_office).through(:country_state) }
+
   it { is_expected.to validate_presence_of(:account).with_message(:required) }
   it { is_expected.not_to validate_presence_of :country_state }
   it { is_expected.to validate_presence_of :first_name }

spec/models/regional_office_spec.rb

@@ -7,6 +7,8 @@ RSpec.describe RegionalOffice do
 
   it { is_expected.to belong_to :country_state }
 
+  it { is_expected.to have_many(:membership_apps).through(:country_state) }
+
   it do
     is_expected.to \
       validate_presence_of(:country_state)