The setup =

I have this class, Transcript:

class Transcript(models.Model):    
    body = models.TextField('Body')
    doPagination = models.BooleanField('Paginate')
    numPages = models.PositiveIntegerField('Number of Pages')

and this class, TranscriptPages(models.Model):

class TranscriptPages(models.Model):
    transcript = models.ForeignKey(Transcript)
    order = models.PositiveIntegerField('Order')
    content = models.TextField('Page Content', null=True, blank=True)

The Admin behavior I’m trying to create is to let a user populate Transcript.body with the entire contents of a long document and, if they set Transcript.doPagination = True and save the Transcript admin, I will automatically split the body into n Transcript pages.

In the admin, TranscriptPages is a StackedInline of the Transcript Admin.

To do this I’m overridding Transcript’s save method:

def save(self):
    if self.doPagination:
        #do stuff
        super(Transcript, self).save()
    else:
        super(Transcript, self).save()

The problem =

When Transcript.doPagination is True, I want to manually delete all of the TranscriptPages that reference this Transcript so I can then create them again from scratch.

So, I thought this would work:

#do stuff   
TranscriptPages.objects.filter(transcript__id=self.id).delete()
super(Transcript, self).save()

but when I try I get this error:

Exception Type: ValidationError Exception Value: [u'Select a valid choice. That choice is not one of the available choices.']

... and this is the last thing in the stack trace before the exception is raised:

.../django/forms/models.py in save_existing_objects

1. pk_value = form.fields[pk_name].clean(raw_pk_value)

Other attempts to fix:

• t = self.transcriptpages_set.all().delete() (where self = Transcript from the save() method)
• looping over t (above) and deleting each item individually
• making a post_save signal on TranscriptPages that calls the delete method

Any ideas? How does the Admin do it?

UPDATE: Every once in a while as I'm playing around with the code I can get a different error (below), but then it just goes away and I can't replicate it again... until the next random time.

Exception Type:
MultiValueDictKeyError Exception Value: "Key 'transcriptpages_set-0-id' not found in " Exception Location: .../django/utils/datastructures.py in getitem, line 203

and the last lines from the trace:

.../django/forms/models.py in _construct_form

1. form = super(BaseInlineFormSet, self)._construct_form(i, **kwargs)

.../django/utils/datastructures.py in getitem

1. pk = self.data[pk_key]