Django form validation and action on two models - django

Question

I haven't got much experience with building custom forms (only default model forms) and I'm looking for some help here. I'm trying to build a form that will get "feed_url" from user and if it already exist, just add reference into UserFeed model. In case it doesn't exist, it should add it to the Feed model and also reference it in UserFeed model as well.
models
class Category(models.Model):
name = models.CharField(unique=False, max_length=64)
user = models.ForeignKey(User)
slug = AutoSlugField(populate_from='name', always_update='True', unique_with='user')
def __unicode__(self):
return self.name
class Meta:
ordering = ('name',)
class Feed(models.Model):
feed_url = models.URLField(unique=True)
def __unicode__(self):
return self.feed_url
class UserFeed(models.Model):
feed = models.ForeignKey(Feed)
title = models.CharField(max_length=64)
category = models.ForeignKey(Category)
user = models.ForeignKey(User)
slug = AutoSlugField(populate_from='title', always_update='True', unique_with='user')
def __unicode__(self):
return self.title
class Meta:
ordering = ('title',)
forms
class UserFeedForm(forms.Form):
feed_url = forms.URLField()
title = forms.CharField(max_length=64)
category = forms.ModelChoiceField(Category)
user = forms.HiddenInput()
views
def addfeed(request):
categories = Category.objects.filter(user=request.user)
feeds = Feed.objects.all()
if request.method == 'POST':
form = UserFeedForm(request.POST)
form.fields['category'].queryset = categories
if form.is_valid():
feed = form.save(commit=False)
if form.fields['feed_url'] in feeds:
##### add to Feed object and add reference to UserFeed object
feed.user = request.user
feed.save()
else:
##### get id from Feed object and add reference to UserFeed object
feed.user = request.user
feed.save()
return HttpResponseRedirect("/reader/manage")
else:
form = UserFeedForm()
form.fields['category'].queryset = categories
context = {'form': form,}
return expand_context_and_render(request, context, 'reader/form.html')
Could anybody please point me in the right direction?
thanks
UPDATE
Now I have updated my view and form as follows:
forms
class UserFeedForm(forms.ModelForm):
feed = forms.URLField()
title = forms.CharField(max_length=64)
category = forms.ModelChoiceField(Category)
user = forms.HiddenInput()
class Meta:
model = UserFeed
fields = ['feed', 'title', 'category']
views
def addfeed(request):
categories = Category.objects.filter(user=request.user)
feeds = Feed.objects.all()
if request.method == 'POST':
form = UserFeedForm(request.POST)
form.fields['category'].queryset = categories
if form.is_valid():
feed = form.cleaned_data.get('feed')
if feed in feeds:
##### get id from Feed and add reference to UserFeed
existing_feed = Feed.objects.get(feed_url=feed)
form.feed = existing_feed.id
form.user = request.user
form.save(commit=True)
else:
##### add to Feed object and then add reference to UserFeed object
Feed.object.create(feed_url=feed)
existing_feed = Feed.objects.get(feed_url=feed)
form.feed = existing_feed.id
form.user = request.user
form.save(commit=True)
return HttpResponseRedirect("/reader/manage")
else:
form = UserFeedForm()
form.fields['category'].queryset = categories
context = {'page_title': page_title,
'form': form,
}
return expand_context_and_render(request, context, 'reader/form.html')
I think I'm getting closer but it still won't work, giving me this error:
"Cannot assign "u'http://feeds.bbci.co.uk/news/rss.xml'": "UserFeed.feed" must be a "Feed" instance."
Any idea how can I fix this?
thanks

Answer 1

Try taking a look at this question, and also inline formsets in the docs.
Additionally in your UserFieldForm, feed is defined as a URLField. So in your view, in this line:
feed = form.get_cleaned_data.get('feed')
your feed variable is simply a string, and not actually a Feed object. This is where your error might be occurring? That's where inline formsets could help you. Also, this line also makes your your if feed in feeds: statement moot, because feed is just a string, whereas feeds is a Queryset of all your Feed instances. I think this will cause your view to always end up in the else block?
I'm new to Django myself but I hope this helps you.

Answer 2

The logic you are looking for is:
Check if the feed exists.
If it exists, fetch it.
If it doesn't create a new feed.
Associate the feed with a UserFeed object.
The get_or_create method does parts 1-3, so you need the following:
if form.is_valid():
obj = form.save(commit=False)
feed = form.cleaned_data.get('feed')
feed_obj, created = Feed.objects.get_or_create(feed_url=feed)
obj.feed = feed_obj
obj.save()
return HttpResponseRedirect("/reader/manage")

Answer 3

I finally got it working like this:
forms
class UserFeedForm(forms.Form):
feed = forms.URLField()
title = forms.CharField(max_length=64)
category = forms.ModelChoiceField(Category)
user = forms.HiddenInput()
class Meta:
model = UserFeed
fields = ['feed', 'title', 'category']
views
def addfeed(request):
user = request.user
categories = Category.objects.filter(user=request.user)
if request.method == 'POST':
form = UserFeedForm(request.POST)
form.fields['category'].queryset = categories
if form.is_valid():
feed = form.cleaned_data['feed']
category = form.cleaned_data['category']
title = form.cleaned_data['title']
feed_obj, created = Feed.objects.get_or_create(feed_url=feed)
obj = UserFeed(feed=feed_obj, title=title, category=category, user=user)
obj.save()
return HttpResponseRedirect("/reader/manage")
else:
form = UserFeedForm()
form.fields['category'].queryset = categories
context = {'page_title': page_title,
'form': form,
}
return expand_context_and_render(request, context, 'reader/form.html')
Both tips from the answers below pointed me in the right direction. Thanks !