Can I create multiple model instances with CreateView? - django

Question

I have a form whose purpose is to let a user add, edit, subtract and reorder songs. JavaScript DOM manipulation lets users add, subtract and reorder songs fields. The reordering is via jQuery UI's sortable interaction. The order of songs is crucial.
HTML field name attribute values are duplicated. I'm not using Django to generate the form.
Assuming there are two songs on submission, Firebug shows the form DOM looking something like this (csrf omitted):
<form method="post" action="/save/">
<ul id="sortable_songs" class="ui-sortable">
<li>
<input type="text" name="title" id="song_txt_1">
<textarea id="more_info_txtarea_1" name="more_info"></textarea>
</li>
<li>
<input type="text" name="title" id="song_txt_2">
<textarea id="more_info_txtarea_2" name="more_info"></textarea>
</li>
</ul>
<button type="submit">save</button>
</form>
Example query string:
title=FOO&more_info=FOO+INFO&title=BAR&more_info=BAR+INFO
The model:
class Song(models.Model):
title = models.CharField(max_length=65)
more_info = models.CharField(max_length=255)
#todo: foreignkey to User
Probably not much data is involved, both in each record and with regard to the number of records per user. Hence I'm assuming it makes sense that, for a given user, when the form is submitted I'll delete all of their song instances in the Song table and create a bunch of new ones according to the form. (As opposed to having to edit existing records and having a db field which indicates song order).
It seems like I shouldn't write my own view so I'm trying Django's generic CreateView, but perhaps unsurprisingly, with the above user input only a model instance with "BAR" and "BAR INFO" is created -no "FOO" instance is made.
Is there a simple way around this?

Answer 1

You should use Formsets, in this way you can manage multiple instances of an object in a simple way, however you need to control some extra variables and format your query string. But all is covered in the documentation.
You will need a order field in your model:
class Song(models.Model):
title = models.CharField(max_length=65)
more_info = models.CharField(max_length=255)
#todo: foreignkey to User
order = models.PositiveIntegerField()
class Meta:
order_by = ['order']
# to ensure database integrity
unique_thogeter = [(user, order)]
you may also need to update your create view,
class SongListCreate(CreateView):
model = Song
def get_context_data(self, *args, **kwargs):
context = super(SongListCreate, self).get_context_data(*args, **kwargs)
# add a song formset to the context
# or a bound formset from validation
return context
def form_valid(self, form):
formset = SongFormset(#post data)
objects = formset.save(commit = False)
objects.update(#user instance,
#and other data you might need like the new orders)
objects.save()
return super(SongListCreate, self).form_valid(form)
This is roughly what you may need to do, working with formsets is quite a bit hard while you get used to.
You may also want to use a custom library to manage the order of the songs easily, like moving up or down, something like django-positions.
Regards.