In Google App Engine, how do I use reference properties between two entities that reference each other?

Question

If I have two types of models that each reference each other, whichever one I try to define first says it does not recognize the referenced other type (because it is defined further down in the file). For example:

class Author(db.Model):
    most_recent_book = db.ReferenceProperty(Book)

class Book(db.Model):
    author = db.ReferenceProperty(Author)

This will claim that the referenced "Book" model is not recognized. If I flip the order, I run into the same issue (except it will say that "Author" is not recognized). How do I get around this?

score 6 · Accepted Answer · answered Feb 17 '10 at 16:18

6

You can use ReferenceProperty without declaring a type as described in this article from AppEngine Tips

answered Feb 17 '10 at 16:18

Adam Crossland

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Thanks for the tip adam, I've tried it with ndb and it works perfectly. Do you know if this is the best way? It seems a little hacky... – user714852 May 30 '12 at 19:59
Downvoted because the the link is broken, rendering the answer useless :( – Mark Simpson Nov 20 '13 at 02:49

In Google App Engine, how do I use reference properties between two entities that reference each other?

1 Answers1