room.rb

require_relative 'patient'

class Room
  class OverCapacityReachedError < RuntimeError; end

  attr_reader :capacity
  attr_accessor :id

  def initialize(attributes = {})
    @capacity = attributes[:capacity]
    @patients = attributes[:patients] || []
  end

  def add_patient(patient)
    if full?
      raise(OverCapacityReachedError, 'The room is full!')
    else
      @patients << patient
      patient.room = self
    end
  end

  def full?
    @patients.length == @capacity
  end
end

first_room = Room.new(capacity: 2)
puts first_room.capacity
second_room = Room.new(capacity: 4)
john = Patient.new(name: 'John', cured: true)
paul = Patient.new(name: 'Paul')
begin
  first_room.add_patient(john)
  first_room.add_patient(paul)
  george = Patient.new(name: 'George')
  first_room.add_patient(george)
  p first_room
rescue Room::OverCapacityReachedError => error
  puts error
  # TODO put george in another room
end
puts john.room