[FIXED] Django generate custom cheque number

Issue

I'm new in django, I want to create custom Cart number that starts with #. When a new record comes into database. #1-1000, #1-1001, #1-9999, .... #2-1000, ...#2-9999 etc.

This is my model
class Cart(models.Model):
    # id = models.CharField(primary_key=True, editable=False, max_length=10)
    user = models.ForeignKey(Customer, on_delete=models.CASCADE, related_name="cart")
    create_date = models.DateField(auto_now_add=True)
    cart_number = models.CharField(max_length=500, default=increment_cart_number, null=True, blank=True)
    total_summa = models.FloatField()
    time = models.TimeField(auto_now_add=True)

The cart_number will be always in range 1000- 9999 so how can I do that with increment_cart_number function?

Solution

def increment_cart_number():
    last_cart_number = Cart.objects.last()
    if last_cart_number.exists():
       last_num = last_cart_number.cart_number.replace('#','').split('-')
       if int(last_num[1]) >= 9999:
          first_number = int(last_num[0]) + 1
          secound_number = 1000
          result = '#' +str(first_number)+ '-' +str(secound_number)
          return result
       elif int(last_num[1]) < 9999:
           secound_number = int(last_num[1]) + 1
           result = '#'+ last_num[0]+ '-' +str(secound_number)
           return result
     else:
         return '#1-1000'

But I suggest to you for more cleaner way and best practice to do it in another way:

Make this field as AutoField and make defalut value 1000 to start from it.

cart_number = models.AutoField(auto_created = True, default=1000)

After that when you want to print this value add '#' to it from frontend that will be better and faster and easier.

Answered By - Hashem