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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 class="prettyprint lang-py"><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): + serializer = SnippetSerializer(data=request.DATA) + 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 class="prettyprint lang-py"><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) + serializer = SnippetSerializer(snippet, data=request.DATA) + 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> +<pre class="prettyprint lang-py"><code>from django.conf.urls import patterns, url +from rest_framework.urlpatterns import format_suffix_patterns +from snippets import views + +urlpatterns = patterns('', + 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 class="prettyprint lang-py"><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 class="prettyprint lang-py"><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 class="prettyprint lang-py"><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> +<p>Next we'll move onto <a href="4-authentication-and-permissions.html">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> + </div><!--/span--> + </div><!--/row--> + </div><!--/.fluid-container--> + </div><!--/.body content--> + + <div id="push"></div> + </div><!--/.wrapper --> + + <footer class="span12"> + <p>Sponsored by <a href="http://dabapps.com/">DabApps</a>.</a></p> + </footer> + + <!-- Le javascript + ================================================== --> + <!-- Placed at the end of the document so the pages load faster --> + <script src="http://django-rest-framework.org/js/jquery-1.8.1-min.js"></script> + <script src="http://django-rest-framework.org/js/prettify-1.0.js"></script> + <script src="http://django-rest-framework.org/js/bootstrap-2.1.1-min.js"></script> + <script> + //$('.side-nav').scrollspy() + var shiftWindow = function() { scrollBy(0, -50) }; + 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> |