How to Create an Auto Increment in Django other than pk

  

Edited
  It seems that the original solution does not work, django (v 1.11) requires that an autofield field has the primary_key=True parameter, an incor- nance, in my view, for what is the parameter? The way is to try to remedy with a function, see if it works, the function can be placed in the models file itself or in a separate file (as long as you import it in models.py )

import datetime
def increment_chamado():
    ultimo = Chamado.objects.all().order_by('id').last()
    if not ultimo:
        return str(datetime.date.today().year) + str(datetime.date.today().month).zfill(2) + '0000'
    ultimo_id = ultimo.chamado_id
    ultimo_int = int(ultimo_id[9:13])
    new_int = ultimo_int+1
    new_id = str(str(datetime.date.today().year)) + str(datetime.date.today().month).zfill(2) + str(new_int).zfill(4)
  return new_id

In models the field that identifies the call would be:

classe Chamado(models.Model):
    chamado_id = models.CharField(max_length = 20, default = 
        increment_chamado, editable=False)

Based on a post from thecstream.org.

  

From this point forward, the "original" answer.

AutoField

Integer field with automatic increment, Primary keys use it automatically. A primary key is automatically added to your template if you do not specify it.

If you add it to your template:

incremento = models.AutoField(primary_key=False)

You will be adding a field of the type you want (auto-increment) to your model.

SQN

AssertionError: A model can't have more than one AutoField.

Solution

Set your own PK over a field that is not autofield

Suggestion

If you do not have a field that can guarantee that it is unique to use as PK make PK to be uuid like this:

id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)

You can use django-sequence-field . Here's an example:

from sequence_field.fields import SequenceField

# Create your models here.

class TestModel(models.Model):

    sequence = SequenceField(
        key='test.sequence.1',
        template='%Y%m%d%(code)s%NNNNN',
        params={'code':'ABC'},
        auto=True
    )

Testing the Model

from my_app.models import TestModel

obj = TestModel()
obj.save()

print obj.sequence # 20140703ABC00001

obj = TestModel()
obj.save()

print obj.sequence # 20140703ABC00002

Alternative

You can do this validation on the same hand too:

def next_sequence():
    _model = Memorando.objects.filter().order_by('-Memo')[:1]
    if _model.count() > 0:
        return int(_model[0].Memo) + 1
    return 0