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POIs it bad practice to return a tuple from a Django Manager method rather than a queryset?
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copied!<p>I have some complex business logic that I have placed in a custom ModelManager. The manager method returns a tuple of values rather than a queryset. Is this considered bad practice? if so, what is the recommended approach. I do not want the logic in the View, and Django has no Service tier. Plus, my logic needs to potentially perform multiple queries.</p> <p>The logic needs to select an Event closest to the current time, plus 3 events either side. When placed in the template, it is helpful to know the closest event as this is the event initially displayed in a full-screen slider.</p> <p>The current call is as follows:</p> <pre><code>closest_event, previous_events, next_events = Event.objects.closest() </code></pre> <p>The logic does currently work fine. I am about to convert my app. to render the Event data as JSON in the template so that I can bootstrap a backbone.js View on page load. I plan to use TastyPie to render a Resource server-side into the template. Before I refactor my code, it would be good to know my current approach is not considered bad practice.</p> <p>This is how my app. currently works:</p> <p>views.py</p> <pre><code>class ClosestEventsListView(TemplateView): template_name = 'events/event_list.html' def get(self, request, *args, **kwargs): context = self.get_context_data(**kwargs) closest_event, previous_events, next_events = Event.objects.closest() context['closest_event'] = closest_event context['previous_events'] = previous_events context['next_events'] = next_events return self.render_to_response(context) </code></pre> <p>models.py</p> <pre><code>from datetime import timedelta from django.db import models from django.utils import timezone from model_utils.models import TimeStampedModel class ClosestEventsManager(models.Manager): def closest(self, **kwargs): """ We are looking for the closest event to now plus the 3 events either side. First select by date range until we have a count of 7 or greater Initial range is 1 day eithee side, then widening by another day, if required Then compare delta for each event data and determine the closest Return closest event plus events either side """ now = timezone.now() range_in_days = 1 size = 0 while size < 7: start_time = now + timedelta(days=-range_in_days) end_time = now + timedelta(days=range_in_days) events = self.filter(date__gte=start_time, date__lte=end_time, **kwargs).select_related() size = events.count() range_in_days += 1 previous_delta = None closest_event = None previous_events = None next_events = None position = 0 for event in events: delta = (event.date - now).total_seconds() delta = delta * -1 if delta < 0 else delta if previous_delta and previous_delta <= delta: # we have found the closest event. Now, based on # position get events either size next_events = events[:position-1] previous_events = events[position:] break previous_delta = delta closest_event = event position += 1 return closest_event, previous_events, next_events class Event(TimeStampedModel): class Meta: ordering = ['-date'] topic = models.ForeignKey(Topic) event_type = models.ForeignKey(EventType) title = models.CharField(max_length=100) slug = models.SlugField() date = models.DateTimeField(db_index=True) end_time = models.TimeField() location = models.ForeignKey(Location) twitter_hashtag = models.CharField(null=True, blank=True, max_length=100) web_link = models.URLField(null=True, blank=True) objects = ClosestEventsManager() def __unicode__(self): return self.title </code></pre>

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