Question

When I try to query foreign keys using get(), I always get None values, even though I know they are set to 1 in the DB. Am I missing something here? Should I do something different to get the foreignkey values?

Here’s what the code looks like:

class Car_to_brand( models.Model ):
    brand_id = models.ForeignKey( Brand, db_column='brand_id' )
    ...

class Brand( models.Model ):
    (id is not defined here but it's the primary key)
    ...

print Car_to_brand.__dict__.get( brand_id )

That would give me {brand_id:None}, but it should be {brand_id:1}.

Answer 1

The problem is that you have named your field brand_id and not brand. get(brand_id) is returning None, because there the key brand_id is not in the dictionary. If you print car.__dict__, you will see that it contains brand_id_id instead.

However, it is highly unusual to access attributes using instance.__dict__.get(). Try the following instead:

class Car( models.Model ):
    brand = models.ForeignKey(Brand) # don't need to set db_column, brand_id is the default


car.brand_id # this is the id of the brand (e.g. 1) that this car is linked to 
car.brand # this is the brand instance