Choices

Part of the Models and the Admin section of Coddy's Django journey. Lesson 4 of 23.

A genre should be one of a few values, not any text. The choices option limits a field to a list, given as an enumeration class. A film site could limit who a movie is for:

class Movie(models.Model):
    class Age(models.TextChoices):
        ALL = "all", "All ages"
        TEEN = "teen", "13 and over"
        ADULT = "adult", "18 and over"

    age = models.CharField(max_length=10, choices=Age, default=Age.ALL)

Each member has the value stored in the database, "teen", and the label people read, "13 and over". In code you write Movie.Age.TEEN, so a typo is an error rather than a new value. The class comes before the field that uses it.

Forms and the admin show the labels in a drop-down and refuse other values; the database itself does not check. movie.get_age_display() returns a row's label.

Challenge

Easy

Give Book a genre:

Inside Book, a choices class Genre: FICTION ("fiction", "Fiction"), SCIFI ("scifi", "Science fiction"), MYSTERY ("mystery", "Mystery"), HISTORY ("history", "History").
A field genre, up to 20 characters, limited to those choices, fiction unless you pick another.

In the Shell tab, try Book.Genre.SCIFI.label.

Try it yourself

from django.db import models


class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.CharField(max_length=100)
    year = models.IntegerField()
    price = models.DecimalField(max_digits=6, decimal_places=2)
    is_read = models.BooleanField(default=False)
    finished = models.DateField(null=True, blank=True)
    summary = models.TextField(blank=True)