Models

Represent your data rows.

Workflow: Add model

Find a good name for your data piece:
```
class Book(models.Model):
```
Add necessary fields: !!! Always add this to every model python class Meta: ordering = ['-created_at']

Properties: Quirks

Use models.DateTimeField(default=timezone.now) instead of models.DateTimeField(auto_now_add=True). Helps with testing.

Workflow: Implementing “Fat Model” logic

Identify logic or validation specific to the data object.
Override the clean() method for custom validation.
Define custom methods for data-centric calculations or state changes.

Override the save() method if logic must trigger on every write.

from django.core.exceptions import ValidationError

class Book(models.Model):
    title = models.CharField(max_length=255)
    is_published = models.BooleanField(default=False)

    def clean(self):
        if self.published_date and self.published_date > timezone.now():
            raise ValidationError("Published date cannot be in the future.")