django一对一关系如何将名称映射到子对象？

Question

除了文档中的一个示例之外,我找不到任何关于django如何选择可以从父对象访问子对象的名称的文档.在他们的示例中,他们执行以下操作:

    class Place(models.Model):
        name = models.CharField(max_length=50)
        address = models.CharField(max_length=80)

        def __unicode__(self):
            return u"%s the place" % self.name

    class Restaurant(models.Model):
        place = models.OneToOneField(Place, primary_key=True)
        serves_hot_dogs = models.BooleanField()
        serves_pizza = models.BooleanField()

        def __unicode__(self):
            return u"%s the restaurant" % self.place.name

    # Create a couple of Places.
    >>> p1 = Place(name='Demon Dogs', address='944 W. Fullerton')
    >>> p1.save()
    >>> p2 = Place(name='Ace Hardware', address='1013 N. Ashland')
    >>> p2.save()

    # Create a Restaurant. Pass the ID of the "parent" object as this object's ID.
    >>> r = Restaurant(place=p1, serves_hot_dogs=True, serves_pizza=False)
    >>> r.save()

    # A Restaurant can access its place.
    >>> r.place
    <Place: Demon Dogs the place>
    # A Place can access its restaurant, if available.
    >>> p1.restaurant

因此在他们的示例中,他们只是在没有明确定义该名称的情况下调用p1.restaurant.Django假设名称以小写开头.如果对象名称有多个单词,如FancyRestaurant,会发生什么？

旁注:我正在尝试以这种方式扩展User对象.可能是问题吗？

Answer 1

如果您定义自定义,related_name那么它将使用它,否则它将小写整个模型名称(在您的示例中.fancyrestaurant).请参阅django.db.models.related代码中的else块:

def get_accessor_name(self):
    # This method encapsulates the logic that decides what name to give an
    # accessor descriptor that retrieves related many-to-one or
    # many-to-many objects. It uses the lower-cased object_name + "_set",
    # but this can be overridden with the "related_name" option.
    if self.field.rel.multiple:
        # If this is a symmetrical m2m relation on self, there is no reverse accessor.
        if getattr(self.field.rel, 'symmetrical', False) and self.model == self.parent_model:
            return None
        return self.field.rel.related_name or (self.opts.object_name.lower() + '_set')
    else:
        return self.field.rel.related_name or (self.opts.object_name.lower())

以下是OneToOneField调用它的方式:

class OneToOneField(ForeignKey):
    ... snip ...

    def contribute_to_related_class(self, cls, related):
        setattr(cls, related.get_accessor_name(),
                SingleRelatedObjectDescriptor(related))

opts.object_name(在django.db.models.related.get_accessor_name中引用)默认为cls.__name__.

至于

旁注:我正在尝试以这种方式扩展User对象.可能是问题吗？

不,它不会,User模型只是一个常规的django模型.请注意related_name碰撞.