How can I Create a List of References in Google App Engine Datastore?

Question

I have a Foo type in my Google App Engine datastore. I'd like it to link to a series of other Foo types, call them prerequisites.

I can use the ListProperty type to make a list of simple value types but I'm not sure how to do this with references. What is the recommended approach for doing this?

Answer 1

References are just keys, which can be represented as strings, so you could use a StringListProperty to store your keys.

Answer 2

There's (currently) no db.ReferenceListProperty in the datastore. You can closely approximate it with a db.ListProperty(db.Key); if you need to retrieve all the referenced keys, you can do a batch db.get() on it to retrieve all the referenced entities at once.