models.py

from django.db import models
from django.urls import reverse


class Publisher(models.Model):
    name = models.CharField(null=False, blank=False, max_length=255)

    def __str__(self):
        return self.name

    def get_absolute_url(self):
        return reverse("books:publisher_detail", kwargs={"pk": self.pk})


class Book(models.Model):
    title = models.CharField(null=False, blank=False, max_length=255)

    publisher = models.ForeignKey(
        "Publisher",
        null=False,
        blank=False,
        on_delete=models.CASCADE,
        related_name="books",
    )

    def __str__(self):
        return self.title


class BookImage(models.Model):
    "e.g. image of the cover, backcover, etc."

    book = models.ForeignKey(
        "Book", null=False, blank=False, on_delete=models.CASCADE, related_name="images"
    )

    image = models.ImageField(null=False, blank=False, max_length=255)

    alt_text = models.CharField(null=False, blank=True, max_length=255)