Extending class, date based generic views in django and get_context_data? - django

Question

I'm trying to extend a simple date based view (using the 1.3 generic class approach) with my own mixin "BaseViewMixin":
class BaseViewMixin(object):
"""define some basic context for our views"""
model = Alert
month_format = "%m"
date_field = "date"
def get_context_data(self, **kwargs):
"""extra context"""
context = super(BaseViewMixin, self).get_context_data(**kwargs)
context["CACHE_SERVERS"] = settings.CACHE_SERVERS
return context
#method_decorator(login_required)
def dispatch(self, *args, **kwargs):
return super(BaseViewMixin, self).dispatch(*args, **kwargs)
class IndexView(BaseViewMixin, TodayArchiveView):
template_name= "index.html"
def get_context_data(self, **kwargs):
context = super(IndexView, self).get_context_data(**kwargs)
queryset = Alert.objects.default(self.day)
tickets = Alert.objects.tickets(self.day)
alert_groups = []
for item in tickets:
alert_groups.append({"ticket": item, "alerts": queryset.filter(ticket=item["ticket"])})
context["alert_groups"] = alert_groups
return context
The problem is that all of the date based things you normally get in the context are wiped out as soon as I override the get_context_data method for my IndexView class. Why is that? I would expect {{ day }}, {{ previous_day }} etc to show up in the context, as well as self. When I remove my get_context_data method all the generic date stuff works.
urls.py entry is just:
url(r'^$', IndexView.as_view(), name='index'),

Answer 1

This is one way to do it which allows me to reuse code. I'm still not understanding why get_context_data wipes out the TodayArchiveView context the way I define it in my original question. It seems that using the scenario below would do the same thing to my mixin but it doesn't. The ViewMixin context is preserved when calling get_context_data in DateMixin.
class ViewMixin(object):
"""define some basic context for our views"""
model = Alert
def get_context_data(self, **kwargs):
"""extra context"""
context = super(ViewMixin, self).get_context_data(**kwargs)
context["CACHE_SERVERS"] = settings.CACHE_SERVERS
return context
#method_decorator(login_required)
def dispatch(self, *args, **kwargs):
return super(ViewMixin, self).dispatch(*args, **kwargs)
class DateMixin(object):
month_format = "%m"
date_field = 'date'
def get_alert_groups(self):
none, qs, dated_items = self.get_dated_items()
day = dated_items["day"]
queryset = Alert.objects.default(day)
tickets = Alert.objects.tickets(day)
alert_groups = []
for item in tickets:
alert_groups.append({"ticket": item, "alerts": queryset.filter(ticket=item["ticket"])})
return alert_groups
def get_context_data(self, **kwargs):
context = super(DateMixin, self).get_context_data(**kwargs)
context["alert_groups"] = self.get_alert_groups()
return context
class IndexView(ViewMixin, DateMixin, TodayArchiveView):
template_name= "index.html"

Answer 2

Not an exact answer to your question, but considering the fact that your goal seems to be adding a certain context to more than one view a context processor might be a good solution!

Answer 3

The problem arise because you're inhereting from 2 classes.
context = super(IndexView, self).get_context_data(**kwargs) will initialise the context with the method from BaseViewMixin not TodayArchiveView (super walks base classes from left to right) --> context variables from TodayArchiveView will be lost.
I think you can do this:
def get_context_data(self, **kwargs):
context = super(IndexView, self).get_context_data(**kwargs)
context_day = super(BaseViewMixin, self).get_context_data(**kwargs)
context = dict(context, **context_day)
...