django自定义非主键自增字段类型(auto increment field)

桃扇骨 2022-06-09 04:24 400阅读 0赞

### 1.django自定义字段类型,实现非主键字段的自增 ###

# -*- 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)
            # 每张表只能设置一个字段为自增长字段，这个字段可以是主键，也可以不是主键，如果不是主键，则必须设置为一种“键(key)”
            # (primary key)也是键(key)的一种，key还包括外键(foreign key)、唯一键(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 ###

当save()后并不能刷新instance,及save后numbering会为空值,需要重写get一次.  
如果您修复了这个问题请留言回复下,谢谢

### 4.bug修复 ###

以一种非常不优雅的方法进行了简单修复,重写了模型的save方法,在save后从新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)