How to inject same context in many different Django views? - django

Question

I want to put info about one object in many views without repeating it in get_context_data in each view. As u understand i need a class with get_context_data inside, that i can mix with other views.
Here in my example i want to see 'some_object' in context of UpdateAnotherObjectView:
class BaseObjectInfoView(View):
def get_context_data(self, **kwargs):
context_data = super(BaseObjectInfoView, self).get_context_data(**kwargs)
context_data['some_object'] = SomeObjects.objects.get(pk=1)
return context_data
class UpdateAnotherObjectView(BaseObjectInfo, UpdateView):
template_name = 'create_object.html'
form_class = AnotherObjectForm
model = AnotherObjects
def get_context_data(self, **kwargs):
context_data = super(UpdateAnotherObjectView, self).get_context_data(**kwargs)
context_data['all_another_objects'] = AnotherObjects.objects.all()
return context_data
it works, but get_context_data is not a part of parent 'View' class. May be i need more special class to inherit from in BaseObjectInfoView?
or maybe better to construct context with another method ?

Answer 1

Mixins don't need to be views, but it helps IDE's if they have the methods they're overriding.
Contexts are handled by django.views.generic.base.ContextMixin (details on this very handy site), So the class-based views way of things would be this:
from django.views import generic
class WebsiteCommonMixin(generic.base.ContextMixin):
page_title = ''
active_menu = None
def get_context_data(self, **kwargs):
context = super(WebsiteCommonMixin, self).get_context_data(**kwargs)
context.update(dict(page_title=self.page_title, active_menu=self.active_menu))
return context
class NewsListView(WebsiteCommonMixin, ListView):
page_title = 'News list'
active_menu = 'News'
model = News
paginate_by = 12
I do this for many projects and the simple views you have to create anyway, are fully declarative. And by simple, I mean that they can consist of mulitple mixins, all doing the hard stuff in either get_queryset, get_context_data or form_valid. More elaborate example, straight from a project:
class FeedbackMixin(object):
message = 'Well Done!'
def __init__(self):
self._message_kwargs = {}
super().__init__()
def add_message_kwarg(self, name, value) -> None:
self._message_kwargs[name] = value
def format_message(self, kwargs) -> str:
return self.message.format(**kwargs)
def generate_message(self) -> None:
msg = self.format_message(self._message_kwargs)
messages.success(getattr(self, 'request'), msg)
class ModelFeedbackMixin(FeedbackMixin, generic.edit.ModelFormMixin):
success_view_name = None
success_url_kwargs = None
def get_success_url_kwargs(self):
return self.success_url_kwargs
def get_success_url(self) -> str:
success_url_kwargs = self.get_success_url_kwargs()
if not self.success_view_name:
url = super().get_success_url()
elif success_url_kwargs is not None:
url = reverse(self.success_view_name, kwargs=success_url_kwargs)
else:
if hasattr(self.object, 'slug'):
url_kwargs = {'slug': self.object.slug}
else:
url_kwargs = {'pk': self.object.pk}
url = reverse(self.success_view_name, kwargs=url_kwargs)
return url
def form_valid(self, form):
response = super().form_valid(form)
self.generate_message()
return response

Answer 2

Maybe this way could be easier to read...
def add_context(func):
# this is a wrapper function
def wrapper(*args, **kwargs):
context_data = func(*args, **kwargs)
context_data['some_object'] = SomeObjects.objects.get(pk=1)
return context_data
return wrapper
class UpdateAnotherObjectView(BaseObjectInfo, UpdateView):
template_name = 'create_object.html'
form_class = AnotherObjectForm
model = AnotherObjects
#add_context
def get_context_data(self, **kwargs):
kwargs['all_another_objects'] = AnotherObjects.objects.all()
return kwargs