On 08/19/2011 03:15 PM, Jacco wrote:
I am having great difficulties in saving nested models in an easy
way.
#Two (almost) identical functions:
def test1():
place = Place(where='Paris')
place is not saved, thus it does not have a primary key (id)
meeting = Meeting(place=place, when='2011-01-01')
You assign non saved instance to a meeting. Probably what happened
internally is that place.pk is copied to meeting.place_id.
place.save()
You saved place. Changes in model are not reflected to referred model.
meeting.save()
You save meeting with still (partially) stale place pk. thus resulting
an exception.
def test2():
place = Place(where='Paris')
meeting = Meeting(place=place, when='2011-01-01')
place.save()
meeting.place = meeting.place #BY setting meeting.place to
itself, it works !!!!!!!!!!!!
You updated your meeting internal structure.
meeting.save()
return meeting
----------------------------------------------------------------------------------------------------------------------------------------------
- Running test1() results in crash "null value in column "place_id"
violates not-null constraint"
- Running test2() results in OK.
- Only difference is the dummy line "meting.place = meeting.place".
Could someone who really understands this explain what is going on?
What's going on that you have done it incorrect order.
place = Place(where='Paris')
place.save() # Place saved, PK assigned.
meeting = Meeting(place=place, when='2011-01-01')
meeting.save() # Meeting saved with correct place.
--
Jani Tiainen
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