错误模型.py姜

Question

在django中创建迁移时出错

在模型.py在

class StateBuyers(models.Model):
    name = models.CharField(max_length=100)

    def __unicode__(self):
        return self.name

    class Meta:
        db_table = "states"

class CountiesBuyers (models.Model):
    state = models.ForeignKey(StateBuyers, on_delete=models.CASCADE)
    name = models.CharField(max_length=100)

    def __unicode__(self):
        return self.name

    class Meta:
        db_table = "counties"


class CityBuyers (models.Model):
    state = models.ForeignKey(StateBuyers, on_delete=models.CASCADE)
    county = models.ForeignKey(CountiesBuyers, on_delete=models.CASCADE)
    name = models.CharField(max_length=100)

    def __unicode__(self):
        return self.name

    class Meta:
        db_table = "cities"

也许我有错误 创建多个的一个实例

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在迁移时抛出此错误 有什么想法吗？。在

migration error

Answer 1

有点离题，但你为什么不按惯例行事呢？在

• 使用单数形式的简单模型名称
• 如果与默认值相同，则不需要额外的参数
• 如果县有州，为什么要复制州？有性能提升吗？在

class NameAsReprMixin(object):
    def __unicode__(self):
        return self.name

class State(models.Model, NameAsReprMixin):
    name = models.CharField(max_length=100)    


class County(models.Model, NameAsReprMixin):
    state = models.ForeignKey(State)
    name = models.CharField(max_length=100)


class City(models.Model, NameAsReprMixin):
    county = models.ForeignKey(County)
    name = models.CharField(max_length=100)


class Buyer(models.Model, NameAsReprMixin):
    name = models.CharField(max_length= 50)
    state = models.ForeignKey(State, related_name="buyers", null=True)
    city = models.ForeignKey(City, related_name="buyers", null=True)
    phone_number = models.CharField(max_length=15)
    email = models.EmailField(max_length= 50)
    notes = models.CharField(max_length=200)

然后：

^{pr2}$