python - I need to create a function for a formatted reference code in django

Question

I'm using the def_save func to format but obviously it's wrong because it increments based on the id.

class Category(models.Model):
    categories = models.CharField(max_length=100)
    shortterm = models.CharField(max_length=20, null=True, blank=True)


class Requestor(models.Model):
   id = models.AutoField(primary_key=True)
   date_filed = models.DateTimeField(auto_now_add=True, null=True,
         verbose_name='date_filed')
   category = models.ForeignKey(Category, on_delete=models.CASCADE,
         null=True, verbose_name="Category")
   **reference_code = models.CharField(max_length=500, verbose_name=(
        'Reference'), default='Auto Assign', blank=True)**


   def save(self):
        date_ref = timezone.localtime(self.date_filed)
        if self.reference_scholarship == 'Auto Assign':
            last_id = Requestor.objects.latest('id')
            curr_id = last_id.pk
            new_id = int(curr_id) + 1
            # self.ticketcode = self.tickettype.ShortTerm + '-' + str(new_id).zfill(4)
            self.reference_scholarship = str(self.category.shortterm) + '-' +date_ref.strftime('%m%d%Y') + '-' +str(new_id).zfill(2)
            super(Requestor, self).save()
        else:
            super(Requestor, self).save()

The result for the reference code should be like this.

id	date_filed	category	reference_code
1	01012021	local	lsp-01012021-1
2	01012021	foreign	fsp-01012021-1
3	01012021	local	lsp-01012021-2

Answer 1

等待大神答复