Models and the ORM: defining your data

A Django model is a Python class that describes a database table — one class attribute per column, with the type of each attribute telling Django (and the eventual database) what kind of data belongs there. This part defines Post, the model the rest of the series builds around.

The Post model

# blog/models.py
from django.db import models
from django.conf import settings

class Post(models.Model):
    title = models.CharField(max_length=200)
    slug = models.SlugField(max_length=200, unique=True)
    content = models.TextField()
    author = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
    published = models.BooleanField(default=False)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ["-created_at"]

    def __str__(self):
        return self.title

Every model inherits from models.Model — that's what gives it a database table, a manager (Post.objects), and everything else the ORM provides. CharField needs max_length because it maps to a fixed-width SQL column; TextField doesn't, since it's meant for unbounded content like a post body.

Field types worth understanding now

• SlugField — a URL-safe version of a title ("My First Post" → "my-first-post"), used for readable URLs in part 10. unique=True stops two posts from ever generating the same URL.
• ForeignKey — a link to another model. settings.AUTH_USER_MODEL points at whichever user model the project uses (almost always Django's built-in User) rather than importing it directly, which keeps this model working even if a project later swaps in a custom user model. on_delete=models.CASCADE means deleting a user deletes their posts too — the other common option, models.SET_NULL, is covered when Comment needs different behavior in part 11.
• auto_now_add vs auto_now — auto_now_add sets the timestamp once, on creation, and never touches it again; auto_now updates it on every save. Mixing these up is how a post's original publish date silently becomes "whenever it was last edited."

Meta and __str__

class Meta: ordering = ["-created_at"] sets the default order every query returns posts in — newest first, without needing .order_by() on every call site. __str__ isn't optional in any meaningful sense: without it, every Post shows up as Post object (1) in the admin (part 7) and the shell, instead of its actual title.