Question

my current App uses a db.ListProperty(db.Key) for a many to many relation for a friendlist.

We have the following scheme:

# previous models
class User(db.Model):
    name = db.StringProperty()
    nickname = db.StringProperty()
    join_date = db.DateProperty(auto_now_add=True)
    party = db.ReferenceProperty(PartyEntry, collection_name='participants')
    def by_name(self, string):
        return self.gql("WHERE name = :name", name=string).get()
    def key_by_name(self, string):
        return self.by_name(string).key()

class FriendList(db.Model):
    owner = db.ReferenceProperty(User)
    friends = db.ListProperty(db.Key)

And a handler that fetches a users friendlist, processes it and displays it:

class Profile_FriendList(WebBase):
    def get(self):
        user = self._auth()
        if user:
            usr_key = User().key_by_name(user.nickname())
            friend_list = friend_lists = FriendList.all().filter('owner', usr_key).fetch(10)
            self.renderskeleton( { 'friendlist': friend_list } ,'friends.html')

I populated a test friendlist with two db.Key() list entries in FriendList.friends.
The s.c. SDK Console (>Interactive Datastorageviewer) diplays me those items:

key1,key2

But if I call this entity FriendList by its key and
print frlst.friends
output: []
Same problem in the handler.
I get no data I can work with.
BUT the data exist.

Fixed: FriendList problem, the called friendlist object wasn’t a query it simply was a new FriendList() object.
Updated code.

Fixed: Complete question solved

usr_key = User().key_by_name(user.nickname())
logging.info(user.nickname())
logging.info(usr_key)
friend_list = FriendList().all().filter("owner", usr_key).fetch(20)
logging.info(friend_list)
logging.info(friend_list[0].friends)
friends = User.get(friend_list[0].friends)
logging.info(friends)
self.renderskeleton( { 'friends': friends } , 'friends.html')

I selected a list of GqlQuery results instead of the “one” I want, what I had to do from there was simply putting the friends’ key list into an User.get() and voilà I had all necessary data.

Answer 1

friend_list = FriendList(owner=usr_key) is not a query, it is creating a new instance of FriendList.

You want: friend_lists = FriendList.all().filter('owner', usr_key).fetch(10).

Other comments:

1. The two methods on User your using for queries should really be class methods:

   @classmethod
   def by_name(cls, string):
       return cls.gql("WHERE name = :name", name=string).get()
   
   @classmethod
   def key_by_name(cls, string):
       return cls.by_name(string).key()
   
   # to call:
   user = User.key_by_name('their name')
   

2. Have you considered using the user’s id with get_by_key_name()? It would be faster than a query.

3. Also use the user’s id as the key_name for the friend-list, then instead of a query you can do friend_list = FriendList.get_by_key_name(str(user.user_id())). You’ll need a way to handle case where one FriendList is not enough, but those will probably be rare — and it is not that difficult to solve (add a sequence number to the key_name and store a (non-indexed) count of the sequences on the User kind, then you can easily generate the key_names).