When saving an object which has a ForeignKey, I get the common error: 'Cannot assign "(myObject)": "(my ForeignKey field)" must be an instance'.
This question is answered clearly:
Django - Foreign Key must be an instance
Django ForeignKey Instance vs Raw ID
but the solutions aren't working for me.
models.py
class User(models.Model):
email = models.EmailField(max_length=100, unique=True)
password = models.CharField(validators=[MinLengthValidator(8)],max_length=60)
is_teacher = models.BooleanField(default=0)
class Question(models.Model):
question_text = models.CharField(max_length=5000)
pub_date = models.DateTimeField('date asked')
answered = models.BooleanField(default=False)
asker = models.IntegerField(default=0)
def __str__(self):
return self.question_text
def was_published_recently(self):
now = timezone.now()
return now - datetime.timedelta(days=1) <= self.pub_date <= now;
def asked_by(self):
return self.asker
class Answer(models.Model):
to_question = ForeignKey(Question, null=False)
pub_date = models.DateTimeField('date answered')
answer_text = models.CharField(max_length=10000)
answered_by = ForeignKey(User, null=False)
def __str__(self):
return self.answer_text
views.py
@staff_member_required()
def answerQuestion(request):
if request.method == 'POST':
form = QuestionAnswerForm(request.POST,label_suffix='',error_class=DivErrorList)
if form.is_valid():
answer_text = request.POST['answer_text']
question_id = request.POST['question_id']
now = timezone.now()
try:
to_question = Question.objects.get(pk=question_id)
answered_by= User.objects.get(pk=request.user.id)
Answer.objects.create(answer_text=answer_text, to_question=to_question, pub_date=now, answered_by=answered_by)
return render(request, 'askWisdom/answerQuestion.html', { 'result':'Thanks for Your Answer' })
except Question.DoesNotExist:
return HttpResponse("Question doesn't exist.")
except User.DoesNotExist:
return HttpResponse("Answering User doesn't exist.")
else:
return render(request, 'askWisdom/answerQuestion.html', {'form': form, 'error_message': form.errors })
The actual error is: 'Cannot assign "User: sampleUser@gmail.com": "Answer.answered_by" must be a "User" instance'.
The strange thing is, my Answer model has two ForeignKeys, but when doing
Answer.objects.create(answer_text=answer_text, to_question=to_question, pub_date=now, answered_by=answered_by)
the error is flagged on the second ForeignKey (answered_by=answered_by) but not the first one (to_question=to_question) assuming they are processed in sequence.
Ok, so change it to force saving a numeric id at the database level:
answered_by_id= User.objects.get(pk=request.user.id).id
Answer.objects.create(answer_text=answer_text, to_question=to_question, pub_date=now, answered_by_id=answered_by_id)
and I get the error: 'column answer.id does not exist'
In this case, there's an actual column in the Postgres database named answered_by_id, so I don't see why it's looking for a hidden, apparently auto-generated 'answer.id' column instead.
But anyway, I'd rather get the default method working of passing an instance to the ForeignKey field.
Is there something obvious I'm overlooking? I'll be embarrassed if it's just a typo.
