I need to create an auto increasing invoice number starting from 000001 and going up ex.000001, 000002, 000003 and so on right now i have this code that i took from another stack overflow question but i dont want the MAG part

    def increment_invoice_number(self):
    last_invoice = Transaction.objects.all().order_by('id').last()
    if not last_invoice:
        return 'MAG0001'
    invoice_no = last_invoice.invoice_no
    invoice_int = int(invoice_no.split('MAG')[-1])
    new_invoice_int = invoice_int   1
    new_invoice_no = 'MAG'   str(new_invoice_int)
    return new_invoice_no

invoice_no = models.CharField(max_length=500, default=increment_invoice_number, null=True, blank=True)

i want my invoice num to start with 000001

CodePudding user response：

You can use an IntegerField instead of a CharField for the invoices:

from django.db.models import Max

def invoice_number():
    invid = Invoice.objects.aggregate(
        max_inv=Max('invoice_no')
    )['max_inv']
    if invid is not None:
        return invid   1
    return 0

class Invoice(models.Model):
    invoice_no = models.IntegerField(default=invoice_number, unique=True, editable=False)

We thus determine the maximum value for invoice_no, and then assign this as default value for the invoice_no of our Invoice model.

unique=True will prevent having two (or more) invoices with the same invoice_no. If there is a race condition, then one of the two views will error on this. You thus can implement a retry mechanism to eventually assign a valid invoice number.

By making it editable=False, this will not appear in the ModelForms and ModelAdmins for the Invoice model. You can omit this if the form should make the field editable.