patient.rb

class Patient
  attr_reader :name, :cured, :id
  attr_accessor :room


  def initialize(attributes)
    @name = attributes[:name]
    @id = attributes[:id].to_i
    @cured = attributes[:cured] || false
  end

  def cure
    @cured = true
  end
end

patients.csv

patients_repository.rb

require 'csv'
require_relative 'patient'
require_relative 'rooms_repository'

class PatientsRepository
  def initialize(csv_file, rooms_repository)
    @rooms_repository = rooms_repository
    @csv_file = csv_file
    @patients = []
    load_csv
  end

  def all
    @patients
  end

  def load_csv
    CSV.foreach(@csv_file, headers: true, header_converters: :symbol) do |row|
      patient = Patient.new(row)
      room_id = row[:room_id].to_i

      room = @rooms_repository.find(room_id)

      room.add_patient(patient)
      @patients << patient
    end
  end
end


rooms_repo = RoomsRepository.new(File.join(__dir__, 'rooms.csv'))

patients_repo = PatientsRepository.new(File.join(__dir__,'patients.csv'), rooms_repo)

bob = patients_repo.all.first

p bob.name
p bob.room.name
p bob.room.patients.map(&:name)

room.rb

require_relative 'patient'

class Room
  attr_reader :size, :name, :patients
  attr_accessor :id

  def initialize(attributes)
    @size = attributes[:size].to_i
    @name = attributes[:name]
    @id = attributes[:id].to_i
    @patients = []
  end

  def add_patient(patient)
    @patients << patient
    patient.room = self
  end
end

rooms.csv

rooms_repository.rb

require 'csv'
require_relative 'room'

class RoomsRepository
  def initialize(csv_file)
    @csv_file = csv_file
    @rooms = []
    load_csv
  end

  def find(id)
    @rooms.find { |r| r.id == id }
  end

  def all
    @rooms
  end

  def load_csv
    @next_id = 0
    
    CSV.foreach(@csv_file, headers: true, header_converters: :symbol) do |row|
      @rooms << Room.new(row)
      @next_id += 1
    end
  end
  
  def save(room)
    room.id = @next_id + 1
    @rooms << room
    CSV.open(@csv_file, 'wb') do |csv|
      csv << ['id', 'name', 'size']
      @rooms.each do |room|
        csv << [room.id, room.name, room.size]
      end
    end
  end
end


# room = Room.new(name: '3z', size: 12)

# repo.save(room)

# p repo.all