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POPopulating a Django formset using a left join
 

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    <p>I have the following models: Topic, UserProfile, UserSubscribedToTopic</p> <p>The last of these looks like this:</p> <pre><code>class UserSubscribedToTopic(models.Model): topic = models.ForeignKey(Topic) user_profile = models.ForeignKey(UserProfile) start_date = models.DateField(null=True, blank=True) </code></pre> <p>I want to show a list of topics to the user, with a checkbox by each. If the user checks a checkbox then I'll use JavaScript to show the 'start date' text field (so for the purposes of this question I just need to show a text field next to the checkbox). If the user has already saved their selection and is revisiting the page I want to populate the form accordingly when it is first rendered.</p> <p>I've attempted to do this using formsets:</p> <pre><code>class SubscribeToTopicForm(ModelForm): class Meta: model = UserSubscribedToTopic fields = ('topic','start_date') widgets = {'topic': CheckboxInput(attrs={'class': 'topic-checkbox'}), 'start_date': TextInput(attrs={'class': 'date','placeholder': 'Start date'})} SubscribeToTopicFormSetBase = modelformset_factory( UserSubscribedToTopic, form=SubscribeToTopicForm, extra = 0) class SubscribeToTopicFormSet(SubscribeToTopicFormSetBase): def add_fields(self, form, index): super(SubscribeToTopicFormSet, self).add_fields(form, index) </code></pre> <p>I almost get what I want if I add the following to my view:</p> <pre><code>topics_formset = SubscribeToTopicFormSet(queryset=UserSubscribedToTopic.objects.filter(user_profile=user.get_profile())) </code></pre> <p>However, obviously this will only show the topics to which the user has already subscribed. To show all the topics I really need to do is a LEFT JOIN on the Topic table. I can't see how to do this in Django without resorting to raw.</p> <p>My questions:</p> <ul> <li>Am I right in thinking it is not possible to specify a queryset for the formset that is generated from a left join? </li> <li>Would it be better to give up on ModelForm and use a formset that I populate manually? </li> <li>Any better approaches?!</li> </ul>
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    1. USMartin Wilson
    1. USMartin Wilson
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