from django.core.exceptions import ImproperlyConfigured from django.core.paginator import InvalidPage, Paginator from django.db.models.query import QuerySet from django.http import Http404 from django.utils.translation import gettext as _ from django.views.generic.base import ContextMixin, TemplateResponseMixin, View class MultipleObjectMixin(ContextMixin): """A mixin for views manipulating multiple objects.""" allow_empty = True queryset = None model = None paginate_by = None paginate_orphans = 0 context_object_name = None paginator_class = Paginator page_kwarg = 'page' ordering = None def get_queryset(self): """ Return the list of items for this view. The return value must be an iterable and may be an instance of `QuerySet` in which case `QuerySet` specific behavior will be enabled. """ if self.queryset is not None: queryset = self.queryset if isinstance(queryset, QuerySet): queryset = queryset.all() elif self.model is not None: queryset = self.model._default_manager.all() else: raise ImproperlyConfigured( "%(cls)s is missing a QuerySet. Define " "%(cls)s.model, %(cls)s.queryset, or override " "%(cls)s.get_queryset()." % { 'cls': self.__class__.__name__ } ) ordering = self.get_ordering() if ordering: if isinstance(ordering, str): ordering = (ordering,) queryset = queryset.order_by(*ordering) return queryset def get_ordering(self): """Return the field or fields to use for ordering the queryset.""" return self.ordering def paginate_queryset(self, queryset, page_size): """Paginate the queryset, if needed.""" paginator = self.get_paginator( queryset, page_size, orphans=self.get_paginate_orphans(), allow_empty_first_page=self.get_allow_empty()) page_kwarg = self.page_kwarg page = self.kwargs.get(page_kwarg) or self.request.GET.get(page_kwarg) or 1 try: page_number = int(page) except ValueError: if page == 'last': page_number = paginator.num_pages else: raise Http404(_('Page is not “last”, nor can it be converted to an int.')) try: page = paginator.page(page_number) return (paginator, page, page.object_list, page.has_other_pages()) except InvalidPage as e: raise Http404(_('Invalid page (%(page_number)s): %(message)s') % { 'page_number': page_number, 'message': str(e) }) def get_paginate_by(self, queryset): """ Get the number of items to paginate by, or ``None`` for no pagination. """ return self.paginate_by def get_paginator(self, queryset, per_page, orphans=0, allow_empty_first_page=True, **kwargs): """Return an instance of the paginator for this view.""" return self.paginator_class( queryset, per_page, orphans=orphans, allow_empty_first_page=allow_empty_first_page, **kwargs) def get_paginate_orphans(self): """ Return the maximum number of orphans extend the last page by when paginating. """ return self.paginate_orphans def get_allow_empty(self): """ Return ``True`` if the view should display empty lists and ``False`` if a 404 should be raised instead. """ return self.allow_empty def get_context_object_name(self, object_list): """Get the name of the item to be used in the context.""" if self.context_object_name: return self.context_object_name elif hasattr(object_list, 'model'): return '%s_list' % object_list.model._meta.model_name else: return None def get_context_data(self, *, object_list=None, **kwargs): """Get the context for this view.""" queryset = object_list if object_list is not None else self.object_list page_size = self.get_paginate_by(queryset) context_object_name = self.get_context_object_name(queryset) if page_size: paginator, page, queryset, is_paginated = self.paginate_queryset(queryset, page_size) context = { 'paginator': paginator, 'page_obj': page, 'is_paginated': is_paginated, 'object_list': queryset } else: context = { 'paginator': None, 'page_obj': None, 'is_paginated': False, 'object_list': queryset } if context_object_name is not None: context[context_object_name] = queryset context.update(kwargs) return super().get_context_data(**context) class BaseListView(MultipleObjectMixin, View): """A base view for displaying a list of objects.""" def get(self, request, *args, **kwargs): self.object_list = self.get_queryset() allow_empty = self.get_allow_empty() if not allow_empty: # When pagination is enabled and object_list is a queryset, # it's better to do a cheap query than to load the unpaginated # queryset in memory. if self.get_paginate_by(self.object_list) is not None and hasattr(self.object_list, 'exists'): is_empty = not self.object_list.exists() else: is_empty = not self.object_list if is_empty: raise Http404(_('Empty list and “%(class_name)s.allow_empty” is False.') % { 'class_name': self.__class__.__name__, }) context = self.get_context_data() return self.render_to_response(context) class MultipleObjectTemplateResponseMixin(TemplateResponseMixin): """Mixin for responding with a template and list of objects.""" template_name_suffix = '_list' def get_template_names(self): """ Return a list of template names to be used for the request. Must return a list. May not be called if render_to_response is overridden. """ try: names = super().get_template_names() except ImproperlyConfigured: # If template_name isn't specified, it's not a problem -- # we just start with an empty list. names = [] # If the list is a queryset, we'll invent a template name based on the # app and model name. This name gets put at the end of the template # name list so that user-supplied names override the automatically- # generated ones. if hasattr(self.object_list, 'model'): opts = self.object_list.model._meta names.append("%s/%s%s.html" % (opts.app_label, opts.model_name, self.template_name_suffix)) elif not names: raise ImproperlyConfigured( "%(cls)s requires either a 'template_name' attribute " "or a get_queryset() method that returns a QuerySet." % { 'cls': self.__class__.__name__, } ) return names class ListView(MultipleObjectTemplateResponseMixin, BaseListView): """ Render some list of objects, set by `self.model` or `self.queryset`. `self.queryset` can actually be any iterable of items, not just a queryset. """