learning_record_recorddinningroom.room_id may not be NULL

Question

I am trying to use Django to build up a model which can record the modification history of another user. Also, i used signal function to save the history model, when the parent model is saved. All other models works well.

The code is like below:

from control.model import DinningRoom`

class RecordDinningRoom(models.Model):
    room = models.ForeignKey(DinningRoom)

    datetime = models.DateTimeField('recordtime', auto_now=True)

    TURN_ON_OFF = (
        ('ON', 'On'),
        ('OFF', 'Off'),
    )

    TEMP = (
        ('HIGH', 'High'),
        ('MEDIUM', 'Medium'),
        ('LOW', 'Low'),
    )

    on_off = models.CharField(max_length=2, choices=TURN_ON_OFF)
    temp = models.CharField(max_length=2, choices=TEMP)

    #signal function: if a user is created, add control livingroom to the user    
def record_dinningroom(sender, instance, created, **kwargs):
    #the object which is saved can be accessed with **kwargs
    dinningroom = instance
    record = RecordDinningRoom(on_off=dinningroom.on_off, temp=dinningroom.temp)
    record.save() 
#    if created:
#        RecordLivingRoom.objects.create(user=instance)
post_save.connect(record_dinningroom, sender=DinningRoom)

And when saving the foreign key model, it jumps to the error page with information "learning_record_recorddinningroom.room_id may not be NULL". I think it could be problems in either the room = models.ForeignKey(DinningRoom) or the signal and record_dinningroom() function, but cannot figure out how to fix it.

Answer 1

You need to set room for RecordDinningRoom as it is not an optional field, try this:

record = RecordDinningRoom(
    on_off=dinningroom.on_off,
    temp=dinningroom.temp,
    room=instance
)