Created
April 15, 2014 21:50
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Easy to use mixin to get a paginated detail page using django's generic views.
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| from django.db.models import Q | |
| from django.db.models.sql.query import get_order_dir | |
| # Taken from: https://gist.github.com/dokterbob/1004216 | |
| def get_next_or_previous(qs, item, next=True): | |
| """ | |
| Get the next or previous object in the queryset, with regards to the | |
| item specified. | |
| """ | |
| # If we want the previous object, reverse the default ordering | |
| if next: | |
| default_ordering = 'ASC' | |
| else: | |
| default_ordering = 'DESC' | |
| # First, determine the ordering. This code is from get_ordering() in | |
| # django.db.sql.compiler | |
| if qs.query.extra_order_by: | |
| ordering = qs.query.extra_order_by | |
| elif not qs.query.default_ordering: | |
| ordering = qs.query.order_by | |
| else: | |
| ordering = qs.query.order_by or qs.query.model._meta.ordering | |
| assert not ordering == '?', 'This makes no sense for random ordering.' | |
| query_filter = None | |
| for field in ordering: | |
| # Account for possible reverse ordering | |
| field, direction = get_order_dir(field, default_ordering) | |
| item_value = getattr(item, field) | |
| # Either make sure we filter increased values or lesser values | |
| # depending on the sort order | |
| if direction == 'ASC': | |
| filter_dict = {'%s__gt' % field: item_value} | |
| else: | |
| filter_dict = {'%s__lt' % field: item_value} | |
| # Make sure we nicely or the conditions for the queryset | |
| if query_filter: | |
| query_filter = query_filter | Q(**filter_dict) | |
| else: | |
| query_filter = Q(**filter_dict) | |
| # Reverse the order if we're looking for previous items | |
| if default_ordering == 'DESC': | |
| qs = qs.reverse() | |
| # Filter the queryset | |
| qs = qs.filter(query_filter) | |
| # Return either the next/previous item or None if not existent | |
| try: | |
| return qs[0] | |
| except IndexError: | |
| return None | |
| class GetNextAndPreviousMixin(object): | |
| ''' | |
| Mix this into a ``django.views.generic.DetailView`` and get a | |
| ``{{ previous_object }}`` and ``{{ next_object }}`` based on the currently | |
| used queryset. So you want probably want to use the same queryset ordering | |
| as in the list view. | |
| ''' | |
| def get_context_data(self, **kwargs): | |
| queryset = self.get_queryset() | |
| kwargs['previous_object'] = get_next_or_previous( | |
| queryset, | |
| self.object, | |
| next=False) | |
| kwargs['next_object'] = get_next_or_previous( | |
| queryset, | |
| self.object, | |
| next=True) | |
| context_object_name = self.get_context_object_name(self.object) | |
| previous_name = 'previous_{}'.format(context_object_name) | |
| next_name = 'next_{}'.format(context_object_name) | |
| kwargs[previous_name] = kwargs['previous_object'] | |
| kwargs[next_name] = kwargs['next_object'] | |
| return super(GetNextAndPreviousMixin, self).get_context_data(**kwargs) |
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