Done

lib/appointment.rb

@@ -0,0 +1,19 @@
+class Appointment
+
+  attr_accessor :date, :patient, :doctor
+
+  @@all = []
+
+  def initialize(date, patient, doctor)
+    @date = date
+    @patient = patient
+    @doctor = doctor
+    @@all << self 
+  end
+
+  def self.all
+    @@all 
+  end 
+
+
+end 

lib/artist.rb

@@ -0,0 +1,27 @@
+class Artist 
+
+  attr_accessor :name 
+
+  @@all = []
+
+  def self.all
+    @@all
+  end 
+
+  def initialize(name)
+    @name = name 
+    @@all << self
+  end 
+
+  def new_song(song, genre)
+    Song.new(song, self, genre)
+  end 
+
+  def songs
+    Song.all.select {|song| song.artist == self}
+  end
+
+  def genres
+    songs.collect {|song| song.genre}
+  end 
+end 

lib/doctor.rb

@@ -0,0 +1,29 @@
+class Doctor
+  attr_accessor :name 
+
+    @@all = []
+
+  def self.all
+    @@all
+  end 
+
+  def initialize(name)
+    @name = name 
+    @@all << self 
+  end 
+
+  def new_appointment(patient, date)
+    Appointment.new(date, patient, self)
+
+  end 
+
+  def appointments
+    Appointment.all.select {|appointment| appointment.doctor == self}
+  end 
+
+  def patients 
+    appointments.collect {|appointment| appointment.patient}
+  end 
+
+
+end 

lib/genre.rb

@@ -0,0 +1,26 @@
+class Genre 
+  attr_accessor :name
+
+  @@all = []
+
+  def self.all 
+    @@all
+  end 
+
+  def initialize(name)
+    @name = name 
+    @@all << self 
+  end 
+
+  def new_song(song, artist)
+    Song.new(song, artist, self)
+  end 
+
+  def songs
+    Song.all.select {|song| song.genre == self}
+  end
+
+  def artists
+    songs.collect {|song| song.artist}
+  end 
+end 

lib/patient.rb

@@ -0,0 +1,27 @@
+class Patient
+
+  attr_accessor :name 
+
+  @@all = []
+
+  def self.all
+    @@all 
+  end 
+
+  def initialize(name)
+    @name = name 
+    @@all << self 
+  end 
+
+  def new_appointment(doctor, date)
+    Appointment.new(date, self, doctor)
+  end 
+
+  def appointments
+    Appointment.all.select {|appointment| appointment.patient == self}
+  end 
+
+  def doctors 
+    appointments.collect {|appointment| appointment.doctor}
+  end 
+end 

lib/song.rb

@@ -0,0 +1,18 @@
+class Song 
+
+  attr_accessor :name, :artist, :genre
+
+  @@all = []
+
+  def self.all
+    @@all
+  end 
+
+  def initialize(name, artist, genre)
+    @name = name
+    @artist = artist
+    @genre = genre 
+    @@all << self 
+  end 
+
+end