1.django自定義欄位型別,實現非主鍵欄位的自增

# -*- encoding: utf-8 -*-

from django.db.models.fields import Field, IntegerField
from django.core import checks, exceptions
from django.utils.translation import ugettext_lazy as _


class AutoIncreField(Field):
    description = _("Integer")

    empty_strings_allowed = False
 

    default_error_messages = {
        'invalid': _("'%(value)s' value must be an integer."),
    }

    def __init__(self, *args, **kwargs):
        kwargs['blank'] = True
        super(AutoIncreField, self).__init__(*args, **kwargs)

    def check(self, **kwargs):
        errors = super(AutoIncreField, self).check(**kwargs)
        # 每張表只能設定一個欄位為自增長欄位，這個欄位可以是主鍵，也可以不是主鍵，如果不是主鍵，則必須設定為一種“鍵(key)”
 

        # (primary key)也是鍵(key)的一種，key還包括外來鍵(foreign key)、唯一鍵(unique key)
        errors.extend(self._check_key())
        return errors

    def _check_key(self):
        if not self.unique:
            return [
                checks.Error(
                    'AutoIncreFields must set key(unique=True).'
 
,
                    obj=self,
                    id='fields.E100',
                ),
            ]
        else:
            return []

    def deconstruct(self):
        name, path, args, kwargs = super(AutoIncreField, self).deconstruct()
        del kwargs['blank']
        kwargs['unique'] = True
        return name, path, args, kwargs

    def get_internal_type(self):
        return "AutoIncreField"

    def to_python(self, value):
        if value is None:
            return value
        try:
            return int(value)
        except (TypeError, ValueError):
            raise exceptions.ValidationError(
                self.error_messages['invalid'],
                code='invalid',
                params={'value': value},
            )

    def db_type(self, connection):
        return 'bigint AUTO_INCREMENT'

    def rel_db_type(self, connection):
        return IntegerField().db_type(connection=connection)

    def validate(self, value, model_instance):
        pass

    def get_db_prep_value(self, value, connection, prepared=False):
        if not prepared:
            value = self.get_prep_value(value)
            value = connection.ops.validate_autopk_value(value)
        return value

    def get_prep_value(self, value):
        value = super(AutoIncreField, self).get_prep_value(value)
        if value is None:
            return None
        return int(value)

    def contribute_to_class(self, cls, name, **kwargs):
        assert not cls._meta.auto_field, "A model can't have more than one AutoIncreField."
        super(AutoIncreField, self).contribute_to_class(cls, name, **kwargs)
        cls._meta.auto_field = self

    def formfield(self, **kwargs):
        return None

2.使用

class Test(models.Model):

    id = models.UUIDField(primary_key=True, default=uuid4)
    numbering = AutoIncreField(_(u'numbering'), unique=True)
    name = models.CharField(_(u'name'), max_length=32, blank=True, null=True)

3.bug

當save()後並不能重新整理instance,及save後numbering會為空值,需要重寫get一次.
如果您修復了這個問題請留言回覆下,謝謝

4.bug修復

以一種非常不優雅的方法進行了簡單修復,重寫了模型的save方法,在save後從新get

class AutoIncreFieldFixMinxin(object):
    def save(self, *args, **kwargs):
        super(AutoIncreFieldFixMinxin, self).save(*args, **kwargs)
        auto_field = self._meta.auto_field.name
        new_obj = self.__class__.objects.get(pk=self.pk)
        setattr(self, auto_field, int(getattr(new_obj, auto_field)))


class Test(AutoIncreFieldFixMinxin, models.Model):
    id = models.UUIDField(primary_key=True, default=uuid4)
    sequence = AutoIncreField(_(u'sequence'), unique=True)
    name = models.CharField(_(u'name'), max_length=100)