Ruby Object Relations: Has-Many-Through Lab

Objectives

1. Write classes that are related to each other via the "has-many-through" relationship.
2. Write methods that use the "has-many-through" relationship to deliver information on related objects.

Overview

In this lab, we'll be dealing with two sets of three classes.

We have a Song, Artist and Genre class. Songs belong to an artist and belong to a genre. A genre has many songs and an artist has many songs. An artist has many genres through its songs and a genre has many artists through its songs.

We also have an Appointment, Doctor and Patient class. Appointments belong to a patient and to a doctor. A doctor has many appointments and a patient has many appointments. A doctor has many patients through its appointments and a patient has many doctor's through its appointments.

Instructions

Start with the Artist/Song/Genre domain.

The Artist model:

• The Artist class needs a class variable @@all that begins as an empty array
• The Artist class needs a class method .all that lists each artist in the class variable
• An artist is initialized with a name and is saved in the @@all array.
• The Artist class needs an instance method, #new_song, that takes in an argument of a name and genre creates a new song. That song should know that it belongs to the artist.
• The Artist class needs an instance method, #songs, that iterates through all songs and finds the songs that belong to that artist. Try using select to achieve this.
• The Artist class needs an instance method, #genres that iterates over that artist's songs and collects the genre of each song.

The Song model:

• The Song class needs a class variable @@all that begins as an empty array.
• The Song class needs a class method .all that lists each artist in the class variable.
• A song should be initialized with a name, an artist, and a genre, and be saved in the @@all array.

The Genre model:

• The Genre class needs a class variable @@all that begins as an empty array.
• The Genre class needs a class method .all that lists each artist in the class variable.
• A genre should be initialized with a name and be saved in the @@all array.
• The Genre class needs an instance method, #new_song, that takes in an argument of a name and an artist and creates a new song. That song should know that it belongs to the genre.
• The Genre class needs an instance method, #songs, that iterates through all songs and finds the songs that belong to that genre.
• The Genre class needs an instance method, #artists, that iterates over the genre's collection of songs and collects the artist that owns each song.

Now let's move on to our Doctor/Appointment/Patient domain model.

The Doctor model:

• The Doctor class needs a class variable @@all that begins as an empty array.
• The Doctor class needs a class method .all that lists each artist in the class variable.
• A doctor should be initialized with a name and be saved in the @@all array.
• The Doctor class needs an instance method, #new_appointment, that takes in a date and an instance of the Patient class and creates a new appointment. That appointment should know that it belongs to the doctor
• The Doctor class needs an instance method, #appointments, that iterates through all appointments and finds those belonging to this doctor.
• The Doctor class needs an instance method, #patients, that iterates over that doctor's appointments and collects the patient that belongs to each appointment.

The Appointment model:

• The Appointment class needs a class variable @@all that begins as an empty array.
• The Appointment class needs a class method .all that lists each artist in the class variable.
• An appointment should be initialized with a date (as a string, like "Monday, August 1st"), a patient, and a doctor. The appointment should be saved in the @@all array.

The Patient model:

• The Patient class needs a class variable @@all that begins as an empty array.
• The Patient class needs a class method .all that lists each artist in the class variable.
• A patient is instantiated with a name and be saved in the @@all array.
• The Patient class needs an instance method, #new_appointment, that takes in an argument of a doctor and a date and creates a new appointment. The appointment should know that it belongs to the patient.
• The Patient class needs an instance method, #appointments, that iterates through the appointments array and returns appointments that belong to the patient.
• The Patient class needs an instance method, #doctors, that iterates over that patient's appointments and collects the doctor that belongs to each appointment.

View Ruby Object Relations: Has-Many-Through Lab on Learn.co and start learning to code for free.

View Has Many Objects Through Lab on Learn.co and start learning to code for free.