CODEWITHSUNDEEP
pythongoogle-app-enginegoogle-cloud-datastoreapp-engine-ndb
Mike
Mike

Reputation: 344

NDB many-to-many KeyProperty kind reference not working

I'm trying to link various entities to each other with KeyProperties in App Engine like this:

class ModelA(ndb.Model):
    mod_bs = ndb.KeyProperty(kind=ModelB, repeated=true)
    mod_cs = ndb.KeyProperty(kind=ModelC, repeated=true)
    # other properties

class ModelB(ndb.Model):
    mod_as = ndb.StringProperty(kind=ModelA, repeated=true)
    mod_cs = ndb.StringProperty(kind=ModelC, repeated=true)
    # other properties

class ModelC(ndb.Model):
    mod_cs = ndb.KeyProperty(kind=ModelA, repeated=true)
    mod_as = ndb.KeyProperty(kind=ModelB, repeated=true)
    # other properties

But I get an error saying that "ModelB" is undefined in this structure. Apparently, anything that is defined below where it is referenced is not recognized. So if I get rid of the kind assignments in ModelA and ModelB, the ones in ModelC are fine and everything runs. I need to reference them circularly, though, and it seems like that should work.

Am I doing something wrong?

Upvotes: 0

Views: 82

Answers (1)

Greg
Greg

Reputation: 10360

In such cases, you can pass the kind as a string:

class ModelA(ndb.Model):
    mod_bs = ndb.KeyProperty(kind='ModelB', repeated=true)
    mod_cs = ndb.KeyProperty(kind='ModelC', repeated=true)
    # other properties

Upvotes: 1

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