Hanami foreig key example

entities.rb

class Student
  include Hanami::Entity
  attributes :teacher_id, …
end

class Teacher
  include Hanami::Entity
  attributes …
end

mappings.rb

collection :students do
  attribute :id, Integer
  attribute :teacher_id, Integer
  …
end

collection :teachers do
  attribute :id, Integer
  …
end

migration.rb

Hanami::Model.migration do
  change do
    create_table :students do
      primary_key :id
      …
      foreign_key :teacher_id, :teachers, null: false
    end
    
    create_table :teachers do
      primary_key :id
      …
    end
  end
end

usage.rb

teacher = TeacherRepository.new.create(Teacher.new)
student = Student.new(teacher_id: teacher.id)
StudentRepository.new.create(student)