This document discusses mixins in Django. Mixins are ordinary Python classes that are used to add additional functionality to other classes through multiple inheritance. They allow code to be reused across multiple classes without needing to extend from a base class. The document explains that mixins are used to improve modularity and reuse features across different classes. It provides an example of creating a LoginRequiredMixin mixin to check if a user is authenticated before dispatching a view. Mixins can be combined with Django's class-based views to add common features like login requirements in a modular way.

1. Demystifying Mixins
with Django

2. @anabalica

3. Mixins are
a controlled
way of adding
functionality
to classes.

4. Mixins are not
special language
constructs.

5. In fact, mixins are
ordinary Python classes.
1 class SomeMixin(object):
2 """My smart mixin"""
3
4 def test_method(self):
5 pass

6. Why use mixins?
to improve modularity

7. When to use mixins?
want to reuse a
particular feature in a lot
of different classes

8. Properties
• single responsibility
• not meant to be extended
• not meant to be instantiated

11. In Python the concept of
mixins is implemented using
multiple inheritance.

12. Order matters

13. 1 class Foo(BaseFoo, SomeMixin):
2 pass
base class mixin

14. 1 class Foo(BaseFoo, SomeMixin):
2 pass

15. 1 class Foo(SomeMixin, BaseFoo):
2 pass

16. 1 # some_app/views.py
2 from django.views.generic import TemplateView
3
4
5 class AboutView(TemplateView):
6 template_name = "about.html"

17. 1 # some_app/views.py
2 from django.views.generic import TemplateView
3
4
5 class AboutView(SomeMixin, TemplateView):
6 template_name = "about.html"

18. My first mixin

19. 1 # some_app/views.py
2
3
4 class LoginRequiredMixin(object):
5

20. 1 # some_app/views.py
2
3
4 class LoginRequiredMixin(object):
5
6 def dispatch(self, request, *args, **kwargs):
7

21. 1 # some_app/views.py
2 from django.core.exceptions import PermissionDenied
3
4
5 class LoginRequiredMixin(object):
6
7 def dispatch(self, request, *args, **kwargs):
8 if not request.user.is_authenticated():
9 raise PermissionDenied
10

22. 1 # some_app/views.py
2 from django.core.exceptions import PermissionDenied
3
4
5 class LoginRequiredMixin(object):
6
7 def dispatch(self, request, *args, **kwargs):
8 if not request.user.is_authenticated():
9 raise PermissionDenied
10
11 return super(LoginRequiredMixin, self).
12 dispatch(request, *args, **kwargs)
13

23. 1 # some_app/views.py
2 from django.views.generic import TemplateView
3
4
5 class AboutView(LoginRequiredMixin, TemplateView):
6 template_name = "about.html"

24. LoginRequiredMixin TemplateView
AboutView

25. LoginRequiredMixin DetailView
AboutView

26. ListView
LoginRequiredListView
AboutView
CreateView
LoginRequiredCreateView
AboutView
DetailView
LoginRequiredDetailView
AboutView
FormView
LoginRequiredFormView
AboutView
MyView
LoginRequiredMyView
AboutView
TemplateView
LoginRequiredTemplateView
AboutView

27. LoginRequiredMixin TemplateView
AboutView

28. dispatch()
get_context_data()
get_template_names()
check if user is logged in,
has permission
add new data to
the context
add more flexibility to
the template names

29. 1 # some_app/views.py
2 from django.views.generic import TemplateView
3
4
5 class AboutView(TemplateView):
6 template_name = "about.html"

30. dispatch()
get_context_data()
get_template_names()
check if user is logged in,
has permission
add new data to
the context
add more flexibility to
the template names

31. docs.djangoproject.com/en/1.8/ref/
class-based-views/base/

32. docs.djangoproject.com/en/1.8/ref/
class-based-views/base/

33. docs.djangoproject.com/en/1.8/topics/
class-based-views/mixins/

34. docs.djangoproject.com/en/1.8/topics/
class-based-views/mixins/

35. ccbv.co.uk/

36. django-braces
Access
Mixins
Form
Mixins
Other
Mixins

37. With great
power comes great
responsibility

38. Recap
• single responsibility
• plug-in functionality
• isn’t creating a subtyping
relation

39. Go back to your views
and start writing mixins
to clean up the code.