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< title > 3 - Class based views< / title >
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< a href = "#tutorial-3-class-based-views" > Tutorial 3: Class Based Views< / a >
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< a href = "#rewriting-our-api-using-class-based-views" > Rewriting our API using class based views< / a >
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< a href = "#using-mixins" > Using mixins< / a >
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< h1 id = "tutorial-3-class-based-views" > Tutorial 3: Class Based Views< / h1 >
< p > We can also write our API views using class based views, rather than function based views. As we'll see this is a powerful pattern that allows us to reuse common functionality, and helps us keep our code < a href = "http://en.wikipedia.org/wiki/Don't_repeat_yourself" > DRY< / a > .< / p >
< h2 id = "rewriting-our-api-using-class-based-views" > Rewriting our API using class based views< / h2 >
< p > We'll start by rewriting the root view as a class based view. All this involves is a little bit of refactoring of < code > views.py< / code > .< / p >
< pre > < code > from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from django.http import Http404
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status
class SnippetList(APIView):
"""
List all snippets, or create a new snippet.
"""
def get(self, request, format=None):
snippets = Snippet.objects.all()
serializer = SnippetSerializer(snippets, many=True)
return Response(serializer.data)
def post(self, request, format=None):
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serializer = SnippetSerializer(data=request.data)
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if serializer.is_valid():
serializer.save()
return Response(serializer.data, status=status.HTTP_201_CREATED)
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
< / code > < / pre >
< p > So far, so good. It looks pretty similar to the previous case, but we've got better separation between the different HTTP methods. We'll also need to update the instance view in < code > views.py< / code > .< / p >
< pre > < code > class SnippetDetail(APIView):
"""
Retrieve, update or delete a snippet instance.
"""
def get_object(self, pk):
try:
return Snippet.objects.get(pk=pk)
except Snippet.DoesNotExist:
raise Http404
def get(self, request, pk, format=None):
snippet = self.get_object(pk)
serializer = SnippetSerializer(snippet)
return Response(serializer.data)
def put(self, request, pk, format=None):
snippet = self.get_object(pk)
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serializer = SnippetSerializer(snippet, data=request.data)
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if serializer.is_valid():
serializer.save()
return Response(serializer.data)
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
def delete(self, request, pk, format=None):
snippet = self.get_object(pk)
snippet.delete()
return Response(status=status.HTTP_204_NO_CONTENT)
< / code > < / pre >
< p > That's looking good. Again, it's still pretty similar to the function based view right now.< / p >
< p > We'll also need to refactor our < code > urls.py< / code > slightly now we're using class based views.< / p >
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< pre > < code > from django.conf.urls import url
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from rest_framework.urlpatterns import format_suffix_patterns
from snippets import views
urlpatterns = [
url(r'^snippets/$', views.SnippetList.as_view()),
url(r'^snippets/(?P< pk> [0-9]+)/$', views.SnippetDetail.as_view()),
]
urlpatterns = format_suffix_patterns(urlpatterns)
< / code > < / pre >
< p > Okay, we're done. If you run the development server everything should be working just as before.< / p >
< h2 id = "using-mixins" > Using mixins< / h2 >
< p > One of the big wins of using class based views is that it allows us to easily compose reusable bits of behaviour.< / p >
< p > The create/retrieve/update/delete operations that we've been using so far are going to be pretty similar for any model-backed API views we create. Those bits of common behaviour are implemented in REST framework's mixin classes.< / p >
< p > Let's take a look at how we can compose the views by using the mixin classes. Here's our < code > views.py< / code > module again.< / p >
< pre > < code > from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import mixins
from rest_framework import generics
class SnippetList(mixins.ListModelMixin,
mixins.CreateModelMixin,
generics.GenericAPIView):
queryset = Snippet.objects.all()
serializer_class = SnippetSerializer
def get(self, request, *args, **kwargs):
return self.list(request, *args, **kwargs)
def post(self, request, *args, **kwargs):
return self.create(request, *args, **kwargs)
< / code > < / pre >
< p > We'll take a moment to examine exactly what's happening here. We're building our view using < code > GenericAPIView< / code > , and adding in < code > ListModelMixin< / code > and < code > CreateModelMixin< / code > .< / p >
< p > The base class provides the core functionality, and the mixin classes provide the < code > .list()< / code > and < code > .create()< / code > actions. We're then explicitly binding the < code > get< / code > and < code > post< / code > methods to the appropriate actions. Simple enough stuff so far.< / p >
< pre > < code > class SnippetDetail(mixins.RetrieveModelMixin,
mixins.UpdateModelMixin,
mixins.DestroyModelMixin,
generics.GenericAPIView):
queryset = Snippet.objects.all()
serializer_class = SnippetSerializer
def get(self, request, *args, **kwargs):
return self.retrieve(request, *args, **kwargs)
def put(self, request, *args, **kwargs):
return self.update(request, *args, **kwargs)
def delete(self, request, *args, **kwargs):
return self.destroy(request, *args, **kwargs)
< / code > < / pre >
< p > Pretty similar. Again we're using the < code > GenericAPIView< / code > class to provide the core functionality, and adding in mixins to provide the < code > .retrieve()< / code > , < code > .update()< / code > and < code > .destroy()< / code > actions.< / p >
< h2 id = "using-generic-class-based-views" > Using generic class based views< / h2 >
< p > Using the mixin classes we've rewritten the views to use slightly less code than before, but we can go one step further. REST framework provides a set of already mixed-in generic views that we can use to trim down our < code > views.py< / code > module even more.< / p >
< pre > < code > from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import generics
class SnippetList(generics.ListCreateAPIView):
queryset = Snippet.objects.all()
serializer_class = SnippetSerializer
class SnippetDetail(generics.RetrieveUpdateDestroyAPIView):
queryset = Snippet.objects.all()
serializer_class = SnippetSerializer
< / code > < / pre >
< p > Wow, that's pretty concise. We've gotten a huge amount for free, and our code looks like good, clean, idiomatic Django.< / p >
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< p > Next we'll move onto < a href = "../4-authentication-and-permissions/" > part 4 of the tutorial< / a > , where we'll take a look at how we can deal with authentication and permissions for our API.< / p >
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if (location.hash) shiftWindow();
window.addEventListener("hashchange", shiftWindow);
$('.dropdown-menu').on('click touchstart', function(event) {
event.stopPropagation();
});
// Dynamically force sidenav to no higher than browser window
$('.side-nav').css('max-height', window.innerHeight - 130);
$(function() {
$(window).resize(function() {
$('.side-nav').css('max-height', window.innerHeight - 130);
});
});
< / script >
< / body >
< / html >
