我有两个 django/python 应用程序，一个在 Django 1.8 和 Python 3.4 上运行，另一个在 Django 1.8 和 Python 2.7 上运行。这些应用程序共享一个数据库并使用一个 python 包，该包包含几个模型，这些模型在几个不同的应用程序中的两个应用程序之间共享。
在 3.4 上运行的应用程序运行良好，但在 2.7 上运行的应用程序抛出 ValueError: Relate Model 'model_reference' cannot be resolved。
在这个伪示例中，包是 core_app，这两个模型位于 core_app 中包含的名为 foobar 和 barfoo 的单独应用程序中。
foobar/models.py
class Model_A(models.Model):
name = TextField()
barfoo/models.py
class Model_B(models.Model):
model_a = ForeignKey('core_app_foobar.Model_A')
这是完整的堆栈跟踪。
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/manager.pyc in manager_method(self, *args, **kwargs)
125 def create_method(name, method):
126 def manager_method(self, *args, **kwargs):
--> 127 return getattr(self.get_queryset(), name)(*args, **kwargs)
128 manager_method.__name__ = method.__name__
129 manager_method.__doc__ = method.__doc__
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/query.pyc in get(self, *args, **kwargs)
326 if self.query.can_filter():
327 clone = clone.order_by()
--> 328 num = len(clone)
329 if num == 1:
330 return clone._result_cache[0]
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/query.pyc in __len__(self)
142
143 def __len__(self):
--> 144 self._fetch_all()
145 return len(self._result_cache)
146
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/query.pyc in _fetch_all(self)
963 def _fetch_all(self):
964 if self._result_cache is None:
--> 965 self._result_cache = list(self.iterator())
966 if self._prefetch_related_lookups and not self._prefetch_done:
967 self._prefetch_related_objects()
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/query.pyc in iterator(self)
236 # Execute the query. This will also fill compiler.select, klass_info,
237 # and annotations.
--> 238 results = compiler.execute_sql()
239 select, klass_info, annotation_col_map = (compiler.select, compiler.klass_info,
240 compiler.annotation_col_map)
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/sql/compiler.pyc in execute_sql(self, result_type)
827 result_type = NO_RESULTS
828 try:
--> 829 sql, params = self.as_sql()
830 if not sql:
831 raise EmptyResultSet
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/sql/compiler.pyc in as_sql(self, with_limits, with_col_aliases, subquery)
376 refcounts_before = self.query.alias_refcount.copy()
377 try:
--> 378 extra_select, order_by, group_by = self.pre_sql_setup()
379 if with_limits and self.query.low_mark == self.query.high_mark:
380 return '', ()
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/sql/compiler.pyc in pre_sql_setup(self)
46 might not have all the pieces in place at that time.
47 """
---> 48 self.setup_query()
49 order_by = self.get_order_by()
50 extra_select = self.get_extra_select(order_by, self.select)
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/sql/compiler.pyc in setup_query(self)
37 if all(self.query.alias_refcount[a] == 0 for a in self.query.tables):
38 self.query.get_initial_alias()
---> 39 self.select, self.klass_info, self.annotation_col_map = self.get_select()
40 self.col_count = len(self.select)
41
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/sql/compiler.pyc in get_select(self)
185 if self.query.default_cols:
186 select_list = []
--> 187 for c in self.get_default_columns():
188 select_list.append(select_idx)
189 select.append((c, None))
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/sql/compiler.pyc in get_default_columns(self, start_alias, opts, from_parent)
522 alias = self.query.join_parent_model(opts, model, start_alias,
523 seen_models)
--> 524 column = field.get_col(alias)
525 result.append(column)
526 return result
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/fields/related.pyc in get_col(self, alias, output_field)
2015
2016 def get_col(self, alias, output_field=None):
-> 2017 return super(ForeignKey, self).get_col(alias, output_field or self.related_field)
2018
2019
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/fields/related.pyc in related_field(self)
1895 @property
1896 def related_field(self):
-> 1897 return self.foreign_related_fields[0]
1898
1899 def get_reverse_path_info(self):
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/fields/related.pyc in foreign_related_fields(self)
1629 @property
1630 def foreign_related_fields(self):
-> 1631 return tuple(rhs_field for lhs_field, rhs_field in self.related_fields)
1632
1633 def get_local_related_value(self, instance):
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/fields/related.pyc in related_fields(self)
1616 def related_fields(self):
1617 if not hasattr(self, '_related_fields'):
-> 1618 self._related_fields = self.resolve_related_fields()
1619 return self._related_fields
1620
/home/ubuntu/moi/local/lib/python2.7/site-packages/django/db/models/fields/related.pyc in resolve_related_fields(self)
1601 raise ValueError('Foreign Object from and to fields must be the same non-zero length')
1602 if isinstance(self.rel.to, six.string_types):
-> 1603 raise ValueError('Related model %r cannot be resolved' % self.rel.to)
1604 related_fields = []
1605 for index in range(len(self.from_fields)):
ValueError: Related model 'core_app_foobar.Model_A' cannot be resolved
请您参考如下方法:
试一试:
class Model_B(models.Model):
model_a = ForeignKey('foobar.Model_A')
不要忘记继承 Django 模型。 (两者)
from django.db import models
To refer to models defined in another application, you can explicitly specify a model with the full application label. For example, if the Manufacturer model above is defined in another application called production, you’d need to use:
