How to access a variable in inherited class based views

Question

I am wondering how to run a reality check to decide which template file to use. How do I access agency_count from AgencyFullView? What I currently have returns type object 'AgencyFullMixin' has no attribute 'agency_count'

class AgencyFullMixin(ContextMixin):

    def get_context_data(self, pk, **kwargs):
        context_data = super(AgencyFullMixin, self).get_context_data(**kwargs)
        agency = Agencies.objects.filter(pk=pk)
        context_data["agency"] = agency
        agency_count = agency.count()
        context_data["agency_count"] = agency_count
        return context_data

class AgencyFullView(TemplateView, AgencyFullMixin):

    if agency_count != 0:    **<<<--- What to put here?**
        template_name = 'community_information_database/agency_full.html'
    else: 
        template_name = 'community_information_database/not_valid.html'

    def get_context_data(self, **kwargs):
        context_data = super(AgencyFullView, self).get_context_data(**kwargs)
        return context_data

The code in AgencyFullView seems to be written right in the body of the class. Is that really the case? Also, there seems to be no agency_count variable in the mixin class either, you have agency_count_test. Mind you that agency_count_test is a local variable and it will go away once the get_context_data() method returns. — Mad Wombat
– Mad Wombat, Commented Sep 6, 2017 at 20:37
You are trying to set your template at the class level based on something that will only be calculated on request. This is not going to work. Your if agency_count != 0 code will only run once at the application start, not for every request and so cannot use this count. — Mad Wombat
– Mad Wombat, Commented Sep 6, 2017 at 20:42
Please post your solution as an answer, instead of adding it to your question. The code you have posted doesn't make sense -- you shouldn't have return outside of a method. — Alasdair
– Alasdair, Commented Sep 7, 2017 at 15:40

Alasdair · Accepted Answer · 2017-09-06 23:38:03Z

3

If you want to access agency_count in another method, then you'll have to set it as an attribute. You could do this in the dispatch method.

class AgencyFullMixin(ContextMixin):
    def dispatch(self, request, *args, **kwargs):
        agencies = Agencies.objects.filter(pk=self.kwargs['pk'])
        self.agency_count = agencies.count()
        return super(AgencyFullMixin, self).dispatch(request, *args, **kwargs)

    def get_context_data(self, **kwargs):
        """
        Add the agency count to the context
        """
        context = super(AgencyFullMixin, self).get_context_data(**kwargs)
        context['agency_count'] = self.agency_count
        return context

You can then access self.agency_count in other methods. To change the template name dynamically, you should override get_template_names.

class AgencyFullView(AgencyFullMixin, TemplateView):
    def get_template_names(self):
        if self.agency_count != 0:
            template = 'community_information_database/agency_full.html'
        else: 
            template = 'community_information_database/not_valid.html'
        return [template]  # nb get_template_names must return a list

edited Sep 6, 2017 at 23:38

answered Sep 6, 2017 at 22:03

Alasdair

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2 Comments

Fish Over a year ago

I get the following error: 'super' object has no attribute 'get'. This line is throwing the error: return super(AgencyFullMixin, self).get(request, *args, **kwargs)

Alasdair Over a year ago

Try changing the order of your classes.

Fish · Accepted Answer · 2017-09-07 16:22:25Z

Fixed: Here's the solution I am using:

class AgencyFullMixin(ContextMixin):

    def get_context_data(self, pk, **kwargs):
        context_data = super(AgencyFullMixin, self).get_context_data(**kwargs)
        agency = Agencies.objects.filter(pk=pk)
        context_data["agency"] = agency
        agency_count = agency.count()
        context_data["agency_count"] = agency_count
        return context_data

class AgencyFullView(TemplateView, AgencyFullMixin):
    def get_template_names(self, **kwargs):
        agency = Agencies.objects.filter(pk=self.kwargs['pk']).filter(pk__isnull=False)
        if agency:
            return 'community_information_database/agency_full.html'
        else:
            return 'community_information_database/not_valid.html'

    def get_context_data(self, **kwargs):
        context_data = super(AgencyFullView, self).get_context_data(**kwargs)
        return context_data

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