django之ReverseOneToOneDescriptor

class ReverseOneToOneDescriptor(object):
    """
    Accessor to the related object on the reverse side of a one-to-one
    relation.

    In the example::

        class Restaurant(Model):
            place = OneToOneField(Place, related_name='restaurant')

    ``place.restaurant`` is a ``ReverseOneToOneDescriptor`` instance.
    """
从类的介绍来看，反向一对一描述子是在目标表的。

class OneToOneField(ForeignKey):
    """
    A OneToOneField is essentially the same as a ForeignKey, with the exception
    that it always carries a "unique" constraint with it and the reverse
    relation always returns the object pointed to (since there will only ever
    be one), rather than returning a list.
    """

    # Field flags
    many_to_many = False
    many_to_one = False
    one_to_many = False
    one_to_one = True

    related_accessor_class = ReverseOneToOneDescriptor
    rel_class = OneToOneRel

#一对一的父类（ForeignField）的贡献到相关类的函数
def contribute_to_related_class(self, cls, related):
        super(ForeignKey, self).contribute_to_related_class(cls, related)
        if self.remote_field.field_name is None:
            self.remote_field.field_name = cls._meta.pk.name
#ForeignField的贡献到相关类的函数
def contribute_to_related_class(self, cls, related):#cls是关联类
        # Internal FK's - i.e., those with a related name ending with '+' -
        # and swapped models don't get a related descriptor.
        if not self.remote_field.is_hidden() and not related.related_model._meta.swapped:
            setattr(cls, related.get_accessor_name(), self.related_accessor_class(related))
            # While 'limit_choices_to' might be a callable, simply pass
            # it along for later - this is too early because it's still
            # model load time.
            if self.remote_field.limit_choices_to:
                cls._meta.related_fkey_lookups.append(self.remote_field.limit_choices_to)

def contribute_to_class(self, cls, name, virtual_only=False):

        super(RelatedField, self).contribute_to_class(cls, name, virtual_only=virtual_only)

        self.opts = cls._meta

        if not cls._meta.abstract:
            if self.remote_field.related_name:
                related_name = force_text(self.remote_field.related_name) % {
                    'class': cls.__name__.lower(),
                    'app_label': cls._meta.app_label.lower()
                }
                self.remote_field.related_name = related_name

            def resolve_related_class(model, related, field):
                field.remote_field.model = related
                field.do_related_class(related, model)
            lazy_related_operation(resolve_related_class, cls, self.remote_field.model, field=self)

#manytomanyfield
def contribute_to_related_class(self, cls, related):
        # Internal M2Ms (i.e., those with a related name ending with '+')
        # and swapped models don't get a related descriptor.
        if not self.remote_field.is_hidden() and not related.related_model._meta.swapped:
            setattr(cls, related.get_accessor_name(), ManyToManyDescriptor(self.remote_field, reverse=True))

 #cls:关联类model
 #related.get_accessor_name()：manytomanyrel对象
 #ManyToManyDescriptor(self.remote_field, reverse=True)为rel关系对象