[FIXED] How can we add Two auto-generated field in one model in Django

Issue

I am in need to create two auto generated field: 1st field is ID and another i am taking position that is equivalent to id or we can say it is also auto generated field in the model.

here is the code in which i am integrating:

class DeviceControlPolicy(models.Model):
    vendor_id = models.ForeignKey(Vendor, on_delete=models.CASCADE)
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=1000)
    # schedule_id = models.ForeignKey(ScheduleClassificationGroup, on_delete=models.CASCADE, null=True, default=None)
    usb_storage_device = models.CharField(max_length=10, default="allow")
    cd_dvd = models.CharField(max_length=10, default="allow")
    portable = models.CharField(max_length=10, default="allow")
    wifi = models.CharField(max_length=10, default="allow")
    bluetooth = models.CharField(max_length=10, default="allow")
    webcam = models.CharField(max_length=10, default="allow")
    serial_port = models.CharField(max_length=10, default="allow")
    usb_port = models.CharField(max_length=10, default="allow")
    local_printer = models.CharField(max_length=10, default="allow")
    network_share = models.CharField(max_length=10, default="allow")
    card_reader = models.CharField(max_length=10, default="allow")
    unknown_device = models.CharField(max_length=10, default="allow")
    position = model.[what do i write here to make it auto generated or equal to id]

    def __str__(self):
        return self.name

please help me out to solve this.

Solution

You can override the save method to set the initial value of position:

class DeviceControlPolicy(models.Model):
    vendor_id = models.ForeignKey(Vendor, on_delete=models.CASCADE)
    id = models.AutoField(primary_key=True)
    name = models.CharField(max_length=100)
    description = models.CharField(max_length=1000)
    # schedule_id = models.ForeignKey(ScheduleClassificationGroup, on_delete=models.CASCADE, null=True, default=None)
    usb_storage_device = models.CharField(max_length=10, default="allow")
    cd_dvd = models.CharField(max_length=10, default="allow")
    portable = models.CharField(max_length=10, default="allow")
    wifi = models.CharField(max_length=10, default="allow")
    bluetooth = models.CharField(max_length=10, default="allow")
    webcam = models.CharField(max_length=10, default="allow")
    serial_port = models.CharField(max_length=10, default="allow")
    usb_port = models.CharField(max_length=10, default="allow")
    local_printer = models.CharField(max_length=10, default="allow")
    network_share = models.CharField(max_length=10, default="allow")
    card_reader = models.CharField(max_length=10, default="allow")
    unknown_device = models.CharField(max_length=10, default="allow")
    position = models.IntegerField(blank=True, null=True)

    def __str__(self):
        return self.name

    def save(self, *args, **kwargs):
       super().save(*args, **kwargs)
       
       if self.position == None:
          self.position = self.id
          # You need to call save two times since the id value is not accessible at creation
          super().save()

Answered By - RedWheelbarrow