Test through through

app/models/city.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class City < ApplicationRecord
+  include ChronoModel::TimeMachine
+
+  validates :name, presence: true
+
+  belongs_to :country
+
+  has_many :schools, dependent: :destroy
+end

app/models/country.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class Country < ApplicationRecord
+  include ChronoModel::TimeMachine
+
+  has_many :cities, dependent: :destroy
+  has_many :schools, through: :cities
+  has_many :students, through: :schools
+
+  validates :name, presence: true
+end

app/models/school.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class School < ApplicationRecord
+  include ChronoModel::TimeMachine
+
+  belongs_to :city
+  has_one :country, through: :city
+
+  has_many :students, dependent: :destroy
+
+  validates :name, presence: true
+end

app/models/student.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class Student < ApplicationRecord
+  include ChronoModel::TimeMachine
+
+  belongs_to :school
+  has_one :city, through: :school
+  has_one :country, through: :city
+
+  validates :name, presence: true
+end

db/migrate/20220519102012_create_schools.rb

@@ -0,0 +1,33 @@
+class CreateSchools < ActiveRecord::Migration[6.1]
+  def change
+    create_table :countries, temporal: true do |t|
+      t.string :name
+
+      t.timestamps
+    end
+
+    create_table :cities, temporal: true do |t|
+      t.references :country
+
+      t.string :name
+
+      t.timestamps
+    end
+
+    create_table :schools, temporal: true do |t|
+      t.references :city
+
+      t.string :name
+
+      t.timestamps
+    end
+
+    create_table :students, temporal: true do |t|
+      t.references :school
+
+      t.string :name
+
+      t.timestamps
+    end
+  end
+end

db/seeds.rb

@@ -6,26 +6,14 @@
 #   movies = Movie.create([{ name: 'Star Wars' }, { name: 'Lord of the Rings' }])
 #   Character.create(name: 'Luke', movie: movies.first)
 
-user = User.create! name: 'John Doe'
-project = user.projects.create! name: 'Project 1'
-unit_a = project.units.create! name: 'Unit A 10 days ago'
+france = Country.create!(name: 'France')
+italy = Country.create!(name: 'Italy')
 
-puts "User, Project, Unit A #{Time.current.iso8601}"
+paris = france.cities.create!(name: 'Paris')
+rome = italy.cities.create!(name: 'Rome')
 
-sleep 3.seconds
+pascal = paris.schools.create!(name: 'B. Pascal')
+galilei = rome.schools.create!(name: 'G. Galilei')
 
-unit_b = project.units.create! name: 'Unit B'
-
-puts "Unit B #{Time.current.iso8601}"
-
-sleep 3.seconds
-
-unit_a.update! name: 'Unit A 5 days ago'
-
-puts "Unit A updated #{Time.current.iso8601}"
-
-sleep 3.seconds
-
-user.update! name: 'Joe Doe'
-
-puts "User updated #{Time.current.iso8601}"
+pascal.students.create!(name: 'Vincent')
+galilei.students.create!(name: 'Mario')