Question

I have a model in Django that looks like this:

class Video(models.Model):
    id = models.CharField(primary_key=True, default=uuid.uuid4().hex[:8], editable=False, max_length=8)
    title = models.TextField(max_length=100, help_text='Insert video title here', verbose_name='Title')

I have a superuser that can create new Videos. I go into the admin view and create a new Video. Lets say I create a Video titled "Video 1". It shows up correctly.

Then, if I create another video called Video 2, I can only see Video 2 in the list of Videos. I looked at the history of Video 2, and here is what it said:

March 25, 2018, 3:37 p.m.   superuser   Added.
March 25, 2018, 3:37 p.m.   superuser   Changed title.

Which means that Video 1 is just being updated to Video 2.

However, if I restart my server, I'm able to see Video 2, and then I'm able to create a different Video. But then the problem persists with this new video.

The way I understand it is that with each server session, I'm only allowed to create a single entry.

Answer 1

Your default is being evaluated once when the server starts and the model is loaded:

class Video(models.Model):
    id = models.CharField(primary_key=True, default=uuid.uuid4().hex[:8], editable=False, max_length=8)

You should define a function that generates the default instead:

def new_id():
    return uuid.uuid4().hex[:8]

class Video(models.Model):
    id = models.CharField(primary_key=True, default=new_id, editable=False, max_length=8)

Since you are truncating the UUID, you should consider whether there is a realistic chance of collisions (especially since it appears that collisions overwrite old data silently). You might be better using the default AutoField primary key or a full UUIDField. You could even add an extra 8-character video_id field to display to users.

Creating a new entry using the Django admin interfaces replaces previous entry

1 个答案: