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<li class="main"><a href="#tutorial-3-class-based-views">Tutorial 3: Class Based Views</a></li>
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<li><a href="#rewriting-our-api-using-class-based-views">Rewriting our API using class based views</a></li>
<li><a href="#using-mixins">Using mixins</a></li>
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<li><a href="#using-generic-class-based-views">Using generic class based views</a></li>
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<h1 id="tutorial-3-class-based-views">Tutorial 3: Class Based Views</h1>
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<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.</p>
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<pre class="prettyprint lang-py"><code>from blog.models import Comment
from blog.serializers import CommentSerializer
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from django.http import Http404
from rest_framework.views import APIView
from rest_framework.response import Response
from rest_framework import status
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class CommentRoot(APIView):
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"""
List all comments, or create a new comment.
"""
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def get(self, request, format=None):
comments = Comment.objects.all()
serializer = CommentSerializer(instance=comments)
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return Response(serializer.data)
def post(self, request, format=None):
serializer = CommentSerializer(request.DATA)
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if serializer.is_valid():
comment = serializer.object
comment.save()
return Response(serializer.serialized, status=status.HTTP_201_CREATED)
return Response(serializer.serialized_errors, status=status.HTTP_400_BAD_REQUEST)
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</code></pre>
<p>So far, so good. It looks pretty similar to the previous case, but we've got better seperation between the different HTTP methods. We'll also need to update the instance view. </p>
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<pre class="prettyprint lang-py"><code>class CommentInstance(APIView):
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"""
Retrieve, update or delete a comment instance.
"""
def get_object(self, pk):
try:
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return Comment.objects.get(pk=pk)
except Comment.DoesNotExist:
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raise Http404
def get(self, request, pk, format=None):
comment = self.get_object(pk)
serializer = CommentSerializer(instance=comment)
return Response(serializer.data)
def put(self, request, pk, format=None):
comment = self.get_object(pk)
serializer = CommentSerializer(request.DATA, instance=comment)
if serializer.is_valid():
comment = serializer.deserialized
comment.save()
return Response(serializer.data)
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return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
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def delete(self, request, pk, format=None):
comment = self.get_object(pk)
comment.delete()
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return Response(status=status.HTTP_204_NO_CONTENT)
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</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 URLconf slightly now we're using class based views.</p>
<pre class="prettyprint lang-py"><code>from django.conf.urls import patterns, url
from rest_framework.urlpatterns import format_suffix_patterns
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from blogpost import views
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urlpatterns = patterns('',
url(r'^$', views.CommentRoot.as_view()),
url(r'^(?P&lt;pk&gt;[0-9]+)$', views.CommentInstance.as_view())
)
urlpatterns = format_suffix_patterns(urlpatterns)
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</code></pre>
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<p>Okay, we're done. If you run the development server everything should be working just as before.</p>
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<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>
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<p>The create/retrieve/update/delete operations that we've been using so far are going to be pretty simliar 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 our views by using the mixin classes.</p>
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<pre class="prettyprint lang-py"><code>from blog.models import Comment
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from blog.serializers import CommentSerializer
from rest_framework import mixins
from rest_framework import generics
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class CommentRoot(mixins.ListModelMixin,
mixins.CreateModelMixin,
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generics.MultipleObjectBaseView):
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model = Comment
serializer_class = CommentSerializer
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def get(self, request, *args, **kwargs):
return self.list(request, *args, **kwargs)
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def post(self, request, *args, **kwargs):
return self.create(request, *args, **kwargs)
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</code></pre>
<p>We'll take a moment to examine exactly what's happening here - We're building our view using <code>MultipleObjectBaseView</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 explictly binding the <code>get</code> and <code>post</code> methods to the appropriate actions. Simple enough stuff so far.</p>
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<pre class="prettyprint lang-py"><code>class CommentInstance(mixins.RetrieveModelMixin,
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mixins.UpdateModelMixin,
mixins.DestroyModelMixin,
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generics.SingleObjectBaseView):
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model = Comment
serializer_class = CommentSerializer
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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)
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</code></pre>
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<p>Pretty similar. This time we're using the <code>SingleObjectBaseView</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.</p>
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<pre class="prettyprint lang-py"><code>from blog.models import Comment
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from blog.serializers import CommentSerializer
from rest_framework import generics
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class CommentRoot(generics.RootAPIView):
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model = Comment
serializer_class = CommentSerializer
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class CommentInstance(generics.InstanceAPIView):
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model = Comment
serializer_class = CommentSerializer
</code></pre>
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<p>Wow, that's pretty concise. We've got a huge amount for free, and our code looks like good, clean, idomatic Django.</p>
<p>Next we'll move onto <a href="4-authentication-permissions-and-throttling">part 4 of the tutorial</a>, where we'll take a look at how we can customize the behavior of our views to support a range of authentication, permissions, throttling and other aspects.</p>
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