Post_99.1.rb

class PatronsRepository
  
  def initialize(db)
    @db = db
  end
  
  def create!(attrs={})
    build_model db.patrons.create!(attrs)
  end
  
  def update!(attrs={})
    build_model db.patrons.update!(patron_type, id, attrs)
  end
  
  def find_by_id(patron_type, id)
    build_model db.patrons.find_by_id(patron_type, id)
  end
  
  private
  
  attr_reader :db
  
  def build_model(row)
    if row
      case row[:patron_type]
      when :adult
      AdultPatron.new(row)
      when :child
      ChildPatron.new(row)
      when :senior
      SeniorPatron.new(row)
      else
        raise ArgumentError.new("Unknown user type: #{row[:patron_type]}")
      end
    end
  end
end