Overview

Hey there, been a while. Let's try picking up from where we stopped, now, shall we?

I would be adding some models to the project so we can upload songs into albums. You might be wondering what models are or so, yeah, it's no big deal. In my definition, I'd say models are abstract instances you create just so you can understand what is going on in your database. The abstraction I'm talking about here is the kind of data you're trying to store in the database, in this case, we want to store albums and songs only, we have to create those models, abstract as instances we can understand. Alright.

Content

Create an app for albums and songs
Create Album and Song model relationship
Migrate the models
Messing around with the models

Create an app for albums and songs

This part is really easy, I explained what an app is, in a Django environment, think of it as a collection of similar functionalities, since an album contains songs, it only makes sense to put them in one place together, don't you agree?

I always get confused in this part, like what name do I give the app, it does not matter what name actually, but while naming things in this business, you want it to be related to what it actually does. I'll just call it box, as in music box. To create the app, navigate to your project directory;

struckchure@cws:~/cws/soundbox$ python3 manage.py startapp box

Now i should have a folder named box in the project folder, with some files in it, the files we need to talk about here is just the models.py, views, and one other file we need to create urls.py file.

Let's start with the models.py file

Create `Album` and `Song` model relationship

To create models in our app, we need to add a few codes to our models.py file in box app, let's get to it.

Album model

# box/models.py

from django.db import models


class Album(models.Model):

    title = models.CharField(max_length=100)
    artist = models.CharField(max_length=100)
    cover_art = models.ImageField(upload_to="/cover-arts")
    year = models.PositiveIntegerField()

Line 1: This brings in the module necessary to create a model
Line 4: We defined a model named Album which inherits from models.Model, this allows the model to be added to the database
Line 6: A field to store album title, CharField is commonly used to store strings, with a required parameter, max_length which specifies the maximum length of the title
Line 7: Same as Line 6
Line 8: cover_art is an ImageField for storing images, obviously, with an optional parameter of where the file should be uploaded in the MEDIA_ROOT
Line 9: An integer field to store the release year of the song, as PositiveIntegerField

Piece of cake, ry? Next is the song model

from django.db import models


class Album(models.Model):

    title = models.CharField(max_length=100)
    artist = models.CharField(max_length=100)
    cover_art = models.ImageField(upload_to="/cover-arts")
    year = models.PositiveIntegerField()


class Song(models.Model):

    album = models.ForeignKey(Album, on_delete=models.CASCADE)
    title = models.CharField(max_length=200)

The only strange line here is;

album = models.ForeignKey(Album, on_delete=models.CASCADE)

This is one of many relationships that exist in all databases, if not all.

ForeignKey is classified as ManyToOne relationship, for example, Many songs can belong To One album, sounds pun-ish, dohh. So we said each song should belong to an album - ForeignKey(Album) Then -> ForeignKey(Album, on_delete=models.CASCADE) says the song should be deleted once the album is also deleted.