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Fix the Broken Order ModelHardFix the Code

4/5

Fix Buggy Code

Description

The following Order model has **several bugs and anti-patterns**. Your task is to identify and fix all the issues. The model should represent an order with line items, a status workflow, and a computed total.

This model has 5 issues: wrong field types, missing constraints, an incorrect property, a bad default, and a Meta class problem.

Issues to Fix

01Fix the price field — FloatField causes rounding errors for currency

02Fix the status field — it should use TextChoices, not a plain CharField with no constraints

03Fix the `total` property — it currently doesn't use `F()` expressions and would fail on empty orders

04Fix the `created_at` field — it uses `auto_now` but should use `auto_now_add`

05Fix the `unique_together` — it should prevent duplicate products in the same order

Example

# Fixed version should:
# - Use DecimalField for price
# - Use TextChoices for status
# - Use aggregate + Coalesce for total
# - Use auto_now_add for created_at
# - Have unique_together = ['order', 'product_name']

Python 3Contains bugs

from django.db import models
from django.conf import settings

class Order(models.Model):
    customer = models.ForeignKey(
        settings.AUTH_USER_MODEL,
        on_delete=models.CASCADE,
        related_name='orders'
    )
    status = models.CharField(max_length=20, default='pending')  # BUG: no validation
    created_at = models.DateTimeField(auto_now=True)  # BUG: wrong auto field
    notes = models.TextField(blank=True)

@property
    def total(self):
        # BUG: doesn't handle empty orders, no F() expression
        total = 0
        for item in self.items.all():
            total += item.price * item.quantity
        return total

def __str__(self):
        return f"Order #{self.pk} — {self.status}"

class OrderItem(models.Model):
    order = models.ForeignKey(Order, on_delete=models.CASCADE, related_name='items')
    product_name = models.CharField(max_length=200)
    price = models.FloatField()  # BUG: use DecimalField for money
    quantity = models.PositiveIntegerField(default=1)

class Meta:
        pass  # BUG: missing unique_together

def __str__(self):
        return f"{self.quantity}x {self.product_name}"

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