On 7/1/14, 1:17 PM, trusted...@gmail.com wrote:
> I have two classes, Artwork and Person. Artwork has a relationship to Person.
> However, when I try to use them, I get an error thrown:
>
> InvalidRequestError: When initializing mapper
> Mapper|Artwork|artwork, expression 'Person' failed to locate a
> name ("name 'Person' is not defined"). If this is a class name,
> consider adding this relationship() to the <class 'model.Artwork'>
> class after both dependent classes have been defined.
>
>
>
> Here are the classes themselves, defined in model/__init__.py
> class Artwork(db.Model, SimpleSerializeMixin):
> id = db.Column(db.Integer, primary_key=True)
> ....
> artist_id = db.Column(db.String(256), db.ForeignKey('person.sub'))
> artist = db.relationship('Person', backref='artworks')
>
> class Person(db.Model, SimpleSerializeMixin):
> sub = db.Column(db.String(256), primary_key=True)
>
>
> I checked with debugger and in
> sqlalchemy/ext/declarative/clsregistry.py (_class_resolver.__call__())
> there is a line:
> x = eval(self.arg, globals(), self._dict)
> No "Person" or "Artwork" or any other class defined in the file are
> present in globals(). self._dict is empty
> So it fails with an NameError exception.
>
> What could be the issue ?
it's usually that the Person code wasn't run, e.g. that the module in
which it is located was not imported, before you tried to use the
Artwork class. All the tables/classes can be introduced to the Python
interpreter in any order, but once you try to "use" the mapping, e.g.
make an object or run a query, it resolves all the links and everything
has to be present.
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