Django Tips #15 Using Mixins With Class-Based Views

I was reading today the book Two Scoops of Django by Audrey and Daniel Roy Greenfeld and found some interesting tips about using class-based views with mixins.

Some general rules to use mixins to compose your own view classes, as suggested by Kenneth Love, which I grabbed from the above mentioned book:

The base view classes provided by Django always go to the right; Mixins go to the left of the base view; Mixins should inherit from python’s built-in object type

Following an example to illustrate the rules:

class FormMessageMixin(object): @property def form_valid_message(self): return NotImplemented form_invalid_message = 'Please correct the errors below.' def form_valid(self, form): messages.success(self.request, self.form_valid_message) return super(FormMessageMixin, self).form_valid(form) def form_invalid(self, form): messages.error(self.request, self.form_invalid_message) return super(FormMessageMixin, self).form_invalid(form) class DocumentCreateView(FormMessageMixin, CreateView): model = Document fields = ('name', 'file') success_url = reverse_lazy('documents') form_valid_message = 'The document was successfully created!'

In a similar way you could reuse the same FormMessageMixin in a UpdateView for example, and also override the default form_invalid_message :

class DocumentUpdateView(FormMessageMixin, UpdateView): model = Document fields = ('name', ) success_url = reverse_lazy('documents') form_valid_message = 'The document was successfully updated!' form_invalid_message = 'There are some errors in the form below.'

Since Django 1.9 we have the built-in mixins LoginRequiredMixin and UserPassesTestMixin . If you are using them in your view classes, they should always go on the far left side, like below:

class DocumentUpdateView(LoginRequiredMixin, FormMessageMixin, UpdateView): model = Document fields = ('name', ) success_url = reverse_lazy('documents') form_valid_message = 'The document was successfully updated!'