python - 解决 Django 模型不同验证的设计模式

Question

我正尝试在 Django 1.6.4 中为我的客户编写应用程序

我对 Django 有丰富的经验，但这个案例对我来说很难解决。

我正在使用 Substituting a custom user model功能和我的 Member 类看起来像(这只是简单的代码片段):

class Member(AbstractBaseUser):
    ...
    date_of_birth = models.DateField()
    height = models.FloatField()
    ...
    REQUIRED_FIELDS = ['date_of_birth', 'height']

My Member 可以定义多个不同国家的地址。每个国家都有自己特定的地址验证或额外的字段，所以我定义了主要的抽象地址和一些子地址:

class COUNTRIES(object):
    POLAND = 'pl'
    GERMANY = 'de'
    @classmethod
    def to_choices(cls):
        return ((cls.POLAND, 'Poland'), (cls.GERMANY, 'Germany'))

class BaseAddress(models.Model):
    class Meta:
        abstract = True
    member = models.ForeignKet(settings.AUTH_USER_MODEL, related_name='+')
    country = models.CharField(max_length=2, choices=COUNTRIES.to_choices)

class AddressPL(BaseAddress):
    street = models.CharField(max_length=80)
    city = models.CharField(max_length=20)
    postal_code = models.CharField(max_length=6, validators=[RegexValidator('^\d{2}-\d{3}$'),])
    def save(self, *args, **kwargs):
        self.country = COUNTRIES.POLAND
        super(AddressPL, self).save(*args, **kwargs)

class AddressDE(BaseAddress):
    street = models.CharField(max_length=80)
    city = models.CharField(max_length=20)
    postal_code = models.CharField(max_length=6, validators=[RegexValidator('^\d{5}$'),])
    def save(self, *args, **kwargs):
        self.country = COUNTRIES.GERMANY
        super(AddressPL, self).save(*args, **kwargs)

如您所见，唯一的变化是 validators 部分的 postal_code 字段。唯一的问题是，在 Member 中，我需要添加如下内容:

class Member(AbstractBaseUser):
    ...
    @property
    def addresses(self):
        from itertools import chain
        addresses_pl = AddressPL.objects.filter(member=self)
        addresses_de = AddressDE.objects.filter(member=self)
        return list(chain(addresses_pl, addresses_de))

基于 431628-how to combine 2 or more querysets

我的问题是。你有什么其他的想法来设计这个吗？我需要提供简单、可扩展的解决方案。也许有使用代理的想法？

Answer 1

我认为concrete inheritance可能是您的问题的候选人:

class Member(AbstractBaseUser):
    ...
    date_of_birth = models.DateField()
    height = models.FloatField()
    ...
    REQUIRED_FIELDS = ['date_of_birth', 'height']

class BaseAddress(models.Model):
    # no abstract = True
    member = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='adresses')
    country = models.CharField(max_length=2, choices=COUNTRIES.to_choices)

class AddressPL(BaseAddress):
    # your custom logic here

class AddressDE(BaseAddress):
    # your custom logic here

然后，如果你想添加一些数据:

m = Member(yourargs)
m.save()

adress1 = AdressPL(yourargs)
adress1.member = m
adress1.save()

adress2 = AdressPL(yourargs)
adress2.member = m
adress2.save()

m = Member.objects.get(pk=m.pk)

m.adresses.all() # will output a list of BaseAdresse instances

这样，添加一种新的地址只是子类化 BaseAdress 的问题。无需更改您的用户模型。

具体继承的缺点是它会在继承模型的数据库查询中添加一个连接。

另外，如果你走这条路，看看django-polymorphic ，它是一个 Django 应用程序，提供了处理具体继承的有用方法。