DRF POST giving NOT NULL constraint failed

Question

In a simple API with Python 3.9, Django 3.1.2 and DRF 3.12.1, got the following models

class Movie(models.Model):
    movieNumber=models.CharField(max_length=10)
    movieCategory=models.CharField(max_length=20)

class MovieWatcher(models.Model):
    firstName = models.CharField(max_length=20)
    lastName = models.CharField(max_length=20)
    middleName = models.CharField(max_length=20)
    email = models.CharField(max_length=20)
    phone = models.CharField(max_length=10)

class Reservation(models.Model): # This model has the relation with the other two.
    movie = models.ForeignKey(Movie,on_delete=models.CASCADE) # CASCADE means that when a Movie is deleted, this reservation must also be deleted.
    movieWatcher = models.OneToOneField(MovieWatcher,on_delete=models.CASCADE)

and the following FBV

@api_view(['POST'])
def save_reservation(request):
    movie=Movie.objects.get(id=request.data['movieId'])
    
    movie_watcher=MovieWatcher()
    movie_watcher.firstName=request.data['firstName']
    movie_watcher.lastName=request.data['lastName']
    movie_watcher.middleName=request.data['middleName']
    movie_watcher.email=request.data['email']
    movie_watcher.phone=request.data['phone']
    movie_watcher.save()

    reservation=Reservation()
    reservation.movie = movie
    reservation.movie_watcher = movie_watcher
    reservation.save()
    return Response(status=status.HTTP_201_CREATED)

To test that endpoint, I created a POST request to http://localhost:8000/saveReservation/

After, clicked in Body. Inside Body, x-www-form-urlencoded.

Here I used as keys: movieId, firstName, lastName, middleName, email and phone. As value for the movieId I add an existing movieId created previously and the user does not exist.

All things considered, I was hoping to get the Status 201 Created.

Yet, I get a Status 500 Internal Server Error and the following error

IntegrityError at /saveReservation/ NOT NULL constraint failed: movieApp_reservation.movieWatcher_id

in the terminal it's possible to see this

Internal Server Error: /saveReservation/
Traceback (most recent call last):
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\sqlite3\base.py", line 413, in execute
    return Database.Cursor.execute(self, query, params)
sqlite3.IntegrityError: NOT NULL constraint failed: movieApp_reservation.movieWatcher_id

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\core\handlers\exception.py", line 47, in inner
    response = get_response(request)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\core\handlers\base.py", line 179, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\views\decorators\csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\views\generic\base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\rest_framework\views.py", line 509, in dispatch
    response = self.handle_exception(exc)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\rest_framework\views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\rest_framework\views.py", line 480, in raise_uncaught_exception
    raise exc
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\rest_framework\views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\rest_framework\decorators.py", line 50, in handler
    return func(*args, **kwargs)
  File "C:\Users\tiago\Desktop\beyond\beyond\beyondMoviesAPI\movieApp\views.py", line 33, in save_reservation
    reservation.save()
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\models\base.py", line 753, in save
    self.save_base(using=using, force_insert=force_insert,
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\models\base.py", line 790, in save_base
    updated = self._save_table(
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\models\base.py", line 895, in _save_table
    results = self._do_insert(cls._base_manager, using, fields, returning_fields, raw)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\models\base.py", line 933, in _do_insert
    return manager._insert(
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\models\manager.py", line 85, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\models\query.py", line 1254, in _insert
    return query.get_compiler(using=using).execute_sql(returning_fields)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\models\sql\compiler.py", line 1397, in execute_sql
    cursor.execute(sql, params)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\utils.py", line 98, in execute
    return super().execute(sql, params)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\utils.py", line 66, in execute
    return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\utils.py", line 75, in _execute_with_wrappers
    return executor(sql, params, many, context)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\utils.py", line 90, in __exit__
    raise dj_exc_value.with_traceback(traceback) from exc_value
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
  File "C:\Users\tiago\Desktop\beyond\venv\lib\site-packages\django\db\backends\sqlite3\base.py", line 413, in execute
    return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: NOT NULL constraint failed: movieApp_reservation.movieWatcher_id
[16/Oct/2020 18:51:00] "POST /saveReservation/ HTTP/1.1" 500 175219

All migrations are applied

Answer 1

You have a typo.

Change reservation.movie_watcher = movie_watcher to reservation.movieWatcher = movie_watcher.

The field of your model is called movieWatcher, not movie_watcher.

It's working as you can see in the next image