Django 1.2 + South 0.7 + django-annoying的AutoOneToOneField导致TypeError: 'LegacyConnection'对象不可迭代

Question

我正在使用Django 1.2的开发版本，搭配South 0.7，还有一个从django-annoying复制过来的AutoOneToOneField。South提示我这个字段没有定义规则，而且新版本的South不再自动识别字段类型。所以我查阅了South的文档，写了以下定义（基本上是OneToOneField规则的完全复制）：

rules = [
  (
    (AutoOneToOneField),
    [],
    {
        "to": ["rel.to", {}],
        "to_field": ["rel.field_name", {"default_attr": "rel.to._meta.pk.name"}],
        "related_name": ["rel.related_name", {"default": None}],
        "db_index": ["db_index", {"default": True}],
    },
  )
]
from south.modelsinspector import add_introspection_rules
add_introspection_rules(rules, ["^myapp"]) 

现在，当我进行架构迁移时，South出现了以下错误。

Traceback (most recent call last):
  File "manage.py", line 11, in <module>
    execute_manager(settings)
  File "django/core/management/__init__.py", line 438, in execute_manager
    utility.execute()
  File "django/core/management/__init__.py", line 379, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "django/core/management/base.py", line 196, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "django/core/management/base.py", line 223, in execute
    output = self.handle(*args, **options)
  File "South-0.7-py2.6.egg/south/management/commands/schemamigration.py", line 92, in handle
    (k, v) for k, v in freezer.freeze_apps([migrations.app_label()]).items()
  File "South-0.7-py2.6.egg/south/creator/freezer.py", line 33, in freeze_apps
    model_defs[model_key(model)] = prep_for_freeze(model)
  File "South-0.7-py2.6.egg/south/creator/freezer.py", line 65, in prep_for_freeze
    fields = modelsinspector.get_model_fields(model, m2m=True)
  File "South-0.7-py2.6.egg/south/modelsinspector.py", line 322, in get_model_fields
    args, kwargs = introspector(field)
  File "South-0.7-py2.6.egg/south/modelsinspector.py", line 271, in introspector
    arg_defs, kwarg_defs = matching_details(field)
  File "South-0.7-py2.6.egg/south/modelsinspector.py", line 187, in matching_details
    if any([isinstance(field, x) for x in classes]):
TypeError: 'LegacyConnection' object is not iterable

这是不是和Django 1.2的最近变化有关？我该如何解决这个问题？

我这样使用这个字段：

class Bar(models.Model):
    foo = AutoOneToOneField("foo.Foo", primary_key=True, related_name="bar")

为了参考，这里是django-tagging中的字段代码：

class AutoSingleRelatedObjectDescriptor(SingleRelatedObjectDescriptor):
    def __get__(self, instance, instance_type=None):
        try:
            return super(AutoSingleRelatedObjectDescriptor, self).__get__(instance, instance_type)
        except self.related.model.DoesNotExist:
            obj = self.related.model(**{self.related.field.name: instance})
            obj.save()
            return obj

class AutoOneToOneField(OneToOneField):
    def contribute_to_related_class(self, cls, related):
        setattr(cls, related.get_accessor_name(), AutoSingleRelatedObjectDescriptor(related))

Answer 1

你的规则有个简单的Python相关问题。在元组（tuple）中，如果里面只有一个项目，你必须加个逗号。

所以把 (AutoOneToOneField) 改成 (AutoOneToOneField,)。

不过说实话，我之前不知道可以在字段里面用方法，而不是用规则。我会应用你的修改，然后提交到django-annoying这个库里。

Answer 2

通过去掉一些规则，并在AutoOneToOneField里添加了以下方法，解决了这个问题：

def south_field_triple(self):
    "Returns a suitable description of this field for South."
    from south.modelsinspector import introspector
    field_class = OneToOneField.__module__ + "." + OneToOneField.__name__
    args, kwargs = introspector(self)
    return (field_class, args, kwargs)

Answer 3

试着把这一行改成这样：

(AutoOneToOneField),

改成：

(AutoOneToOneField,),

你这样声明的元组是不能被遍历的。