Trying to see how DDD can help in modeling ATS's Education model.

education.rb

# Entity - Represent an important domain concept with identity and life cycle.
class Education

  def initialize(institution, course, when)
    @institution = Institution.new(institution) # Institution is an Value Object that is immutable
    @course = Course.for(course)                # Course is an Value Object too
    @period = period(when)                      # PostgreSQL's daterange Range Type
  end

  def course_ended? # Query method - Based on period, is CA still studying?
  end

  def source        # Query method - from social profile (LinkedIn) or self-enter
  end
  
  def attributes    # Convenient hash for JSON serialization
    { institution: institution.name, course: course }
  end

end

education_store.rb

# Repository
class EducationStore < ActiveRecord::Base
  include StoreFactory # This factory will convert AR data model to domain model
  
  # Persist
  def self.add(education)
    new(education.attributes).save
  end

  def self.add_all(educations)
  end

  # Finder
  def self.education_by_id(id)
    find(id)
  end

  def self.educations_by_institution(institution)
    where(name: institution.name)
  end

  def self.educations_by_ids(ids)
    where(id: ids)
  end
  
end

institution.rb

# Value Object
# One instance of "NTU" is the same as another instance of "NTU"
# Measure, describe, quantify
class Institution

  def initialize(country, name)
    @country = Country.find(country)
    @name = name
  end

  # Side-Effect-Free function
  def replace(name)
    new(@country, name)
  end

  def ==(other)
    @name == other
  end

end

# Or simply
class Institution < Struct.new(:country, :name)
end