在将 ListField 保存到 GAE 数据存储区时，我得到“属性标签不受支持的类型：”
GAE 数据存储区接收到一个生成器对象以保存到数据库中：
name: 'tags'
value: <generator object <genexpr> at 0x049C6620>
dbindexer\compiler.py 或 djangotoolbox\db\basecompiler.py 可能是从传递给它的列表对象生成这个对象。
(<djangotoolbox.fields.ListField object at 0x047A4070>, [1L])]
关于可能出现的问题的任何提示？
from django.db import models
from djangotoolbox.fields import ListField
class Tag(models.Model):
name = models.CharField(max_length=255)
class Note(models.Model):
tags = ListField(db.ForeignKey(Tag))
例外：
Django Version: 1.3.1
Exception Type: DatabaseError
Exception Value: Unsupported type for property tags: <type 'generator'>
Exception Location: google_appengine\google\appengine\api\datastore_types.py in ValidateProperty, line 1529
File "myapp\django\db\models\base.py" in save
462. self.save_base(using=using, force_insert=force_insert, force_update=force_update)
File "myapp\django\db\models\base.py" in save_base
573. result = manager._insert(values, return_id=update_pk, using=using)
File "myapp\django\db\models\manager.py" in _insert
195. return insert_query(self.model, values, **kwargs)
File "myapp\django\db\models\query.py" in insert_query
1438. return query.get_compiler(using=using).execute_sql(return_id)
File "myapp\dbindexer\compiler.py" in execute_sql
38. return super(SQLInsertCompiler, self).execute_sql(return_id=return_id)
File "myapp\djangotoolbox\db\basecompiler.py" in execute_sql
549. key = self.insert(field_values, return_id=return_id)
File "myapp\djangoappengine\db\compiler.py" in _func
68. return func(*args, **kwargs)
File "myapp\djangoappengine\db\compiler.py" in insert
387. entity.update(properties)
File "google_appengine\google\appengine\api\datastore.py" in update
890. self.__setitem__(name, value)
File "google_appengine\google\appengine\api\datastore.py" in __setitem__
868. datastore_types.ValidateProperty(name, value)
File "google_appengine\google\appengine\api\datastore_types.py" in ValidateProperty
1529. 'Unsupported type for property %s: %s' % (name, v.__class__))
生成器对象由 djangotoolbox 生成，但 GAE 不接受生成器类型。来自 djangotoolbox/db/base.py 的代码
def _value_for_db_collection(self, value, field, field_kind, db_type,
lookup):
# Do convert filter parameters.
if lookup:
# Special case where we are looking for an empty list
if lookup == 'exact' and db_type == 'list' and value == u'[]':
return []
value = self._value_for_db(value, subfield,
subkind, db_subtype, lookup)
# Convert list/set items or dict values.
else:
if field_kind == 'DictField':
# Generator yielding pairs with converted values.
value = (
(key, self._value_for_db(subvalue, subfield,
subkind, db_subtype, lookup))
for key, subvalue in value.iteritems())
# Return just a dict, a once-flattened list;
if db_type == 'dict':
return dict(value)
elif db_type == 'list':
return list(item for pair in value for item in pair)
else:
# Generator producing converted items.
value = (
self._value_for_db(subvalue, subfield,
subkind, db_subtype, lookup)
for subvalue in value)
# "list" may be used for SetField.
if db_type in 'list':
return list(value)
elif db_type == 'set':
# assert field_kind != 'ListField'
return set(value)
# Pickled formats may be used for all collection fields,
# the fields "natural" type is serialized (something
# concrete is needed, pickle can't handle generators :-)
if db_type == 'bytes':
return pickle.dumps(field._type(value), protocol=2)
elif db_type == 'string':
return pickle.dumps(field._type(value))
# If nothing matched, pass the generator to the back-end.
return value
尝试验证上述生成器并引发错误的 AppEngine 代码：
def ValidateProperty(name, values, read_only=False):
ValidateString(name, 'property name', datastore_errors.BadPropertyError)
values_type = type(values)
if values_type is tuple:
raise datastore_errors.BadValueError('May not use tuple property value; property %s is %s.' %(name, repr(values)))
**if values_type is not list:
values = [values]**
if not values:
raise datastore_errors.BadValueError(
'May not use the empty list as a property value; property %s is %s.' %
(name, repr(values)))
try:
for v in values:
prop_validator = _VALIDATE_PROPERTY_VALUES.get(v.__class__)
if prop_validator is None:
raise datastore_errors.BadValueError(
'Unsupported type for property %s: %s' % (name, v.__class__))
prop_validator(name, v)
except (KeyError, ValueError, TypeError, IndexError, AttributeError), msg:
raise datastore_errors.BadValueError(
'Error type checking values for property %s: %s' % (name, msg))