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Pastebin tutorial

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docs/tutorial/1-serialization.md
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@ -2,7 +2,9 @@
## Introduction
This tutorial will walk you through the building blocks that make up REST framework. It'll take a little while to get through, but it'll give you a comprehensive understanding of how everything fits together.
This tutorial will cover creating a simple pastebin code highlighting Web API. Along the way it will introduce the various components that make up REST framework, and give you a comprehensive understanding of how everything fits together.
The tutorial is fairly in-depth, so you should probably get a cookie and a cup of your favorite brew before getting started. If you just want a quick overview, you should head over to the [quickstart] documentation instead.
## Setting up a new environment
@ -17,6 +19,7 @@ Now that we're inside a virtualenv environment, we can install our package requi
pip install django
pip install djangorestframework
pip install pygments # We'll be using this for the code highlighting
**Note:** To exit the virtualenv environment at any time, just type `deactivate`. For more information see the [virtualenv documentation][virtualenv].
@ -30,8 +33,9 @@ To get started, let's create a new project to work with.
cd tutorial
Once that's done we can create an app that we'll use to create a simple Web API.
We're going to create a project that
python manage.py startapp blog
python manage.py startapp snippets
The simplest way to get up and running will probably be to use an `sqlite3` database for the tutorial. Edit the `tutorial/settings.py` file, and set the default database `"ENGINE"` to `"sqlite3"`, and `"NAME"` to `"tmp.db"`.
@ -46,32 +50,48 @@ The simplest way to get up and running will probably be to use an `sqlite3` data
}
}
We'll also need to add our new `blog` app and the `rest_framework` app to `INSTALLED_APPS`.
We'll also need to add our new `snippets` app and the `rest_framework` app to `INSTALLED_APPS`.
INSTALLED_APPS = (
...
'rest_framework',
'blog'
'snippets'
)
We also need to wire up the root urlconf, in the `tutorial/urls.py` file, to include our blog views.
We also need to wire up the root urlconf, in the `tutorial/urls.py` file, to include our snippet views.
urlpatterns = patterns('',
url(r'^', include('blog.urls')),
url(r'^', include('snippets.urls')),
)
Okay, we're ready to roll.
## Creating a model to work with
For the purposes of this tutorial we're going to start by creating a simple `Comment` model that is used to store comments against a blog post. Go ahead and edit the `blog` app's `models.py` file.
For the purposes of this tutorial we're going to start by creating a simple `Snippet` model that is used to store code snippets. Go ahead and edit the `snippets` app's `models.py` file.
from django.db import models
class Comment(models.Model):
email = models.EmailField()
content = models.CharField(max_length=200)
from pygments.lexers import get_all_lexers
from pygments.styles import get_all_styles
LANGUAGE_CHOICES = sorted([(item[1][0], item[0]) for item in get_all_lexers()])
STYLE_CHOICES = sorted((item, item) for item in list(get_all_styles()))
class Snippet(models.Model):
created = models.DateTimeField(auto_now_add=True)
title = models.CharField(max_length=100, default='')
code = models.TextField()
linenos = models.BooleanField(default=False)
language = models.CharField(choices=LANGUAGE_CHOICES,
default='python',
max_length=100)
style = models.CharField(choices=STYLE_CHOICES,
default='friendly',
max_length=100)
class Meta:
ordering = ('created',)
Don't forget to sync the database for the first time.
@ -79,28 +99,40 @@ Don't forget to sync the database for the first time.
## Creating a Serializer class
We're going to create a simple Web API that we can use to edit these comment objects with. The first thing we need is a way of serializing and deserializing the objects into representations such as `json`. We do this by declaring serializers that work very similarly to Django's forms. Create a file in the `blog` directory named `serializers.py` and add the following.
The first thing we need to get started on our Web API is provide a way of serializing and deserializing the snippet instances into representations such as `json`. We can do this by declaring serializers that work very similarly to Django's forms. Create a file in the `snippets` directory named `serializers.py` and add the following.
from blog import models
from django.forms import widgets
from rest_framework import serializers
from snippets import models
class CommentSerializer(serializers.Serializer):
id = serializers.IntegerField(readonly=True)
email = serializers.EmailField()
content = serializers.CharField(max_length=200)
created = serializers.DateTimeField(readonly=True)
class SnippetSerializer(serializers.Serializer):
pk = serializers.Field() # Note: `Field` is an untyped read-only field.
title = serializers.CharField(required=False,
max_length=100)
code = serializers.CharField(widget=widgets.Textarea,
max_length=100000)
linenos = serializers.BooleanField(required=False)
language = serializers.ChoiceField(choices=models.LANGUAGE_CHOICES,
default='python')
style = serializers.ChoiceField(choices=models.STYLE_CHOICES,
default='friendly')
def restore_object(self, attrs, instance=None):
"""
Create or update a new comment instance.
Create or update a new snippet instance.
"""
if instance:
instance.email = attrs['email']
instance.content = attrs['content']
instance.created = attrs['created']
# Update existing instance
instance.title = attrs['title']
instance.code = attrs['code']
instance.linenos = attrs['linenos']
instance.language = attrs['language']
instance.style = attrs['style']
return instance
return models.Comment(**attrs)
# Create new instance
return models.Snippet(**attrs)
The first part of serializer class defines the fields that get serialized/deserialized. The `restore_object` method defines how fully fledged instances get created when deserializing data.
@ -112,31 +144,27 @@ Before we go any further we'll familiarise ourselves with using our new Serializ
python manage.py shell
Okay, once we've got a few imports out of the way, we'd better create a few comments to work with.
Okay, once we've got a few imports out of the way, let's create a code snippet to work with.
from blog.models import Comment
from blog.serializers import CommentSerializer
from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser
c1 = Comment(email='leila@example.com', content='nothing to say')
c2 = Comment(email='tom@example.com', content='foo bar')
c3 = Comment(email='anna@example.com', content='LOLZ!')
c1.save()
c2.save()
c3.save()
snippet = Snippet(code='print "hello, world"\n')
snippet.save()
We've now got a few comment instances to play with. Let's take a look at serializing one of those instances.
We've now got a few snippet instances to play with. Let's take a look at serializing one of those instances.
serializer = CommentSerializer(instance=c1)
serializer = SnippetSerializer(instance=snippet)
serializer.data
# {'id': 1, 'email': u'leila@example.com', 'content': u'nothing to say', 'created': datetime.datetime(2012, 8, 22, 16, 20, 9, 822774, tzinfo=<UTC>)}
# {'pk': 1, 'title': u'', 'code': u'print "hello, world"\n', 'linenos': False, 'language': u'python', 'style': u'friendly'}
At this point we've translated the model instance into python native datatypes. To finalise the serialization process we render the data into `json`.
content = JSONRenderer().render(serializer.data)
content
# '{"id": 1, "email": "leila@example.com", "content": "nothing to say", "created": "2012-08-22T16:20:09.822"}'
# '{"pk": 1, "title": "", "code": "print \\"hello, world\\"\\n", "linenos": false, "language": "python", "style": "friendly"}'
Deserialization is similar. First we parse a stream into python native datatypes...
@ -147,28 +175,45 @@ Deserialization is similar. First we parse a stream into python native datatype
...then we restore those native datatypes into to a fully populated object instance.
serializer = CommentSerializer(data)
serializer = SnippetSerializer(data)
serializer.is_valid()
# True
serializer.object
# <Comment: Comment object>
# <Snippet: Snippet object>
Notice how similar the API is to working with forms. The similarity should become even more apparent when we start writing views that use our serializer.
## Writing regular Django views using our Serializers
## Using ModelSerializers
Our `SnippetSerializer` class is replicating a lot of information that's also contained in the `Snippet` model. It would be nice if we could keep out code a bit more concise.
In the same way that Django provides both `Form` classes and `ModelForm` classes, REST framework includes both `Serializer` classes, and `ModelSerializer` classes.
Let's look at refactoring our serializer using the `ModelSerializer` class.
Open the file `snippets/serializers.py` again, and edit the `SnippetSerializer` class.
class SnippetSerializer(serializers.ModelSerializer):
class Meta:
model = models.Snippet
fields = ('pk', 'title', 'code', 'linenos', 'language', 'style')
## Writing regular Django views using our Serializer
Let's see how we can write some API views using our new Serializer class.
For the moment we won't use any of REST framework's other features, we'll just write the views as regular Django views.
We'll start off by creating a subclass of HttpResponse that we can use to render any data we return into `json`.
Edit the `blog/views.py` file, and add the following.
Edit the `snippet/views.py` file, and add the following.
from blog.models import Comment
from blog.serializers import CommentSerializer
from django.http import HttpResponse
from django.views.decorators.csrf import csrf_exempt
from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser
from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
class JSONResponse(HttpResponse):
"""
@ -181,67 +226,65 @@ Edit the `blog/views.py` file, and add the following.
super(JSONResponse, self).__init__(content, **kwargs)
The root of our API is going to be a view that supports listing all the existing comments, or creating a new comment.
The root of our API is going to be a view that supports listing all the existing snippets, or creating a new snippet.
@csrf_exempt
def comment_root(request):
def snippet_list(request):
"""
List all comments, or create a new comment.
List all code snippets, or create a new snippet.
"""
if request.method == 'GET':
comments = Comment.objects.all()
serializer = CommentSerializer(instance=comments)
snippets = Snippet.objects.all()
serializer = SnippetSerializer(instance=snippets)
return JSONResponse(serializer.data)
elif request.method == 'POST':
data = JSONParser().parse(request)
serializer = CommentSerializer(data)
serializer = SnippetSerializer(data)
if serializer.is_valid():
comment = serializer.object
comment.save()
serializer.save()
return JSONResponse(serializer.data, status=201)
else:
return JSONResponse(serializer.errors, status=400)
Note that because we want to be able to POST to this view from clients that won't have a CSRF token we need to mark the view as `csrf_exempt`. This isn't something that you'd normally want to do, and REST framework views actually use more sensible behavior than this, but it'll do for our purposes right now.
We'll also need a view which corresponds to an individual comment, and can be used to retrieve, update or delete the comment.
We'll also need a view which corresponds to an individual snippet, and can be used to retrieve, update or delete the snippet.
@csrf_exempt
def comment_instance(request, pk):
def snippet_detail(request, pk):
"""
Retrieve, update or delete a comment instance.
Retrieve, update or delete a code snippet.
"""
try:
comment = Comment.objects.get(pk=pk)
except Comment.DoesNotExist:
snippet = Snippet.objects.get(pk=pk)
except Snippet.DoesNotExist:
return HttpResponse(status=404)
if request.method == 'GET':
serializer = CommentSerializer(instance=comment)
serializer = SnippetSerializer(instance=snippet)
return JSONResponse(serializer.data)
elif request.method == 'PUT':
data = JSONParser().parse(request)
serializer = CommentSerializer(data, instance=comment)
serializer = SnippetSerializer(data, instance=snippet)
if serializer.is_valid():
comment = serializer.object
comment.save()
serializer.save()
return JSONResponse(serializer.data)
else:
return JSONResponse(serializer.errors, status=400)
elif request.method == 'DELETE':
comment.delete()
snippet.delete()
return HttpResponse(status=204)
Finally we need to wire these views up. Create the `blog/urls.py` file:
Finally we need to wire these views up. Create the `snippet/urls.py` file:
from django.conf.urls import patterns, url
urlpatterns = patterns('blog.views',
url(r'^$', 'comment_root'),
url(r'^(?P<pk>[0-9]+)$', 'comment_instance')
urlpatterns = patterns('snippets.views',
url(r'^snippet/$', 'snippet_list'),
url(r'^snippet/(?P<pk>[0-9]+)/$', 'snippet_detail')
)
It's worth noting that there's a couple of edge cases we're not dealing with properly at the moment. If we send malformed `json`, or if a request is made with a method that the view doesn't handle, then we'll end up with a 500 "server error" response. Still, this'll do for now.
@ -260,5 +303,6 @@ Our API views don't do anything particularly special at the moment, beyond serve
We'll see how we can start to improve things in [part 2 of the tutorial][tut-2].
[quickstart]: quickstart.md
[virtualenv]: http://www.virtualenv.org/en/latest/index.html
[tut-2]: 2-requests-and-responses.md

45
docs/tutorial/2-requests-and-responses.md
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@ -38,27 +38,27 @@ Okay, let's go ahead and start using these new components to write a few views.
We don't need our `JSONResponse` class anymore, so go ahead and delete that. Once that's done we can start refactoring our views slightly.
from blog.models import Comment
from blog.serializers import CommentSerializer
from rest_framework import status
from rest_framework.decorators import api_view
from rest_framework.response import Response
from snippet.models import Snippet
from snippet.serializers import SnippetSerializer
@api_view(['GET', 'POST'])
def comment_root(request):
def snippet_list(request):
"""
List all comments, or create a new comment.
List all snippets, or create a new snippet.
"""
if request.method == 'GET':
comments = Comment.objects.all()
serializer = CommentSerializer(instance=comments)
snippets = Snippet.objects.all()
serializer = SnippetSerializer(instance=snippets)
return Response(serializer.data)
elif request.method == 'POST':
serializer = CommentSerializer(request.DATA)
serializer = SnippetSerializer(request.DATA)
if serializer.is_valid():
comment = serializer.object
comment.save()
serializer.save()
return Response(serializer.data, status=status.HTTP_201_CREATED)
else:
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
@ -67,30 +67,29 @@ We don't need our `JSONResponse` class anymore, so go ahead and delete that. On
Our instance view is an improvement over the previous example. It's a little more concise, and the code now feels very similar to if we were working with the Forms API. We're also using named status codes, which makes the response meanings more obvious.
@api_view(['GET', 'PUT', 'DELETE'])
def comment_instance(request, pk):
def snippet_detail(request, pk):
"""
Retrieve, update or delete a comment instance.
Retrieve, update or delete a snippet instance.
"""
try:
comment = Comment.objects.get(pk=pk)
except Comment.DoesNotExist:
snippet = Snippet.objects.get(pk=pk)
except Snippet.DoesNotExist:
return Response(status=status.HTTP_404_NOT_FOUND)
if request.method == 'GET':
serializer = CommentSerializer(instance=comment)
serializer = SnippetSerializer(instance=snippet)
return Response(serializer.data)
elif request.method == 'PUT':
serializer = CommentSerializer(request.DATA, instance=comment)
serializer = SnippetSerializer(request.DATA, instance=snippet)
if serializer.is_valid():
comment = serializer.object
comment.save()
serializer.save()
return Response(serializer.data)
else:
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
elif request.method == 'DELETE':
comment.delete()
snippet.delete()
return Response(status=status.HTTP_204_NO_CONTENT)
This should all feel very familiar - there's not a lot different to working with regular Django views.
@ -103,20 +102,20 @@ To take advantage of the fact that our responses are no longer hardwired to a si
Start by adding a `format` keyword argument to both of the views, like so.
def comment_root(request, format=None):
def snippet_list(request, format=None):
and
def comment_instance(request, pk, format=None):
def snippet_detail(request, pk, format=None):
Now update the `urls.py` file slightly, to append a set of `format_suffix_patterns` in addition to the existing URLs.
from django.conf.urls import patterns, url
from rest_framework.urlpatterns import format_suffix_patterns
urlpatterns = patterns('blog.views',
url(r'^$', 'comment_root'),
url(r'^(?P<pk>[0-9]+)$', 'comment_instance')
urlpatterns = patterns('snippet.views',
url(r'^$', 'snippet_list'),
url(r'^(?P<pk>[0-9]+)$', 'snippet_detail')
)
urlpatterns = format_suffix_patterns(urlpatterns)

88
docs/tutorial/3-class-based-views.md
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@ -6,61 +6,59 @@ We can also write our API views using class based views, rather than function ba
We'll start by rewriting the root view as a class based view. All this involves is a little bit of refactoring.
from blog.models import Comment
from blog.serializers import CommentSerializer
from snippet.models import Snippet
from snippet.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 CommentRoot(APIView):
class SnippetList(APIView):
"""
List all comments, or create a new comment.
List all snippets, or create a new snippet.
"""
def get(self, request, format=None):
comments = Comment.objects.all()
serializer = CommentSerializer(instance=comments)
snippets = Snippet.objects.all()
serializer = SnippetSerializer(instance=snippets)
return Response(serializer.data)
def post(self, request, format=None):
serializer = CommentSerializer(request.DATA)
serializer = SnippetSerializer(request.DATA)
if serializer.is_valid():
comment = serializer.object
comment.save()
serializer.save()
return Response(serializer.data, status=status.HTTP_201_CREATED)
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
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.
class CommentInstance(APIView):
class SnippetDetail(APIView):
"""
Retrieve, update or delete a comment instance.
Retrieve, update or delete a snippet instance.
"""
def get_object(self, pk):
try:
return Comment.objects.get(pk=pk)
except Comment.DoesNotExist:
return Snippet.objects.get(pk=pk)
except Snippet.DoesNotExist:
raise Http404
def get(self, request, pk, format=None):
comment = self.get_object(pk)
serializer = CommentSerializer(instance=comment)
snippet = self.get_object(pk)
serializer = SnippetSerializer(instance=snippet)
return Response(serializer.data)
def put(self, request, pk, format=None):
comment = self.get_object(pk)
serializer = CommentSerializer(request.DATA, instance=comment)
snippet = self.get_object(pk)
serializer = SnippetSerializer(request.DATA, instance=snippet)
if serializer.is_valid():
comment = serializer.object
comment.save()
serializer.save()
return Response(serializer.data)
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
def delete(self, request, pk, format=None):
comment = self.get_object(pk)
comment.delete()
snippet = self.get_object(pk)
snippet.delete()
return Response(status=status.HTTP_204_NO_CONTENT)
That's looking good. Again, it's still pretty similar to the function based view right now.
@ -69,11 +67,11 @@ We'll also need to refactor our URLconf slightly now we're using class based vie
from django.conf.urls import patterns, url
from rest_framework.urlpatterns import format_suffix_patterns
from blogpost import views
from snippetpost import views
urlpatterns = patterns('',
url(r'^$', views.CommentRoot.as_view()),
url(r'^(?P<pk>[0-9]+)$', views.CommentInstance.as_view())
url(r'^$', views.SnippetList.as_view()),
url(r'^(?P<pk>[0-9]+)$', views.SnippetDetail.as_view())
)
urlpatterns = format_suffix_patterns(urlpatterns)
@ -88,16 +86,16 @@ The create/retrieve/update/delete operations that we've been using so far are go
Let's take a look at how we can compose our views by using the mixin classes.
from blog.models import Comment
from blog.serializers import CommentSerializer
from snippet.models import Snippet
from snippet.serializers import SnippetSerializer
from rest_framework import mixins
from rest_framework import generics
class CommentRoot(mixins.ListModelMixin,
class SnippetList(mixins.ListModelMixin,
mixins.CreateModelMixin,
generics.MultipleObjectBaseView):
model = Comment
serializer_class = CommentSerializer
model = Snippet
serializer_class = SnippetSerializer
def get(self, request, *args, **kwargs):
return self.list(request, *args, **kwargs)
@ -109,12 +107,12 @@ We'll take a moment to examine exactly what's happening here - We're building ou
The base class provides the core functionality, and the mixin classes provide the `.list()` and `.create()` actions. We're then explicitly binding the `get` and `post` methods to the appropriate actions. Simple enough stuff so far.
class CommentInstance(mixins.RetrieveModelMixin,
mixins.UpdateModelMixin,
mixins.DestroyModelMixin,
generics.SingleObjectBaseView):
model = Comment
serializer_class = CommentSerializer
class SnippetDetail(mixins.RetrieveModelMixin,
mixins.UpdateModelMixin,
mixins.DestroyModelMixin,
generics.SingleObjectBaseView):
model = Snippet
serializer_class = SnippetSerializer
def get(self, request, *args, **kwargs):
return self.retrieve(request, *args, **kwargs)
@ -131,23 +129,23 @@ Pretty similar. This time we're using the `SingleObjectBaseView` class to provi
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.
from blog.models import Comment
from blog.serializers import CommentSerializer
from snippet.models import Snippet
from snippet.serializers import SnippetSerializer
from rest_framework import generics
class CommentRoot(generics.ListCreateAPIView):
model = Comment
serializer_class = CommentSerializer
class SnippetList(generics.ListCreateAPIView):
model = Snippet
serializer_class = SnippetSerializer
class CommentInstance(generics.RetrieveUpdateDestroyAPIView):
model = Comment
serializer_class = CommentSerializer
class SnippetDetail(generics.RetrieveUpdateDestroyAPIView):
model = Snippet
serializer_class = SnippetSerializer
Wow, that's pretty concise. We've got a huge amount for free, and our code looks like good, clean, idiomatic Django.
Next we'll move onto [part 4 of the tutorial][tut-4], 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.
Next we'll move onto [part 4 of the tutorial][tut-4], where we'll take a look at how we can deal with authentication and permissions for our API.
[dry]: http://en.wikipedia.org/wiki/Don't_repeat_yourself
[tut-4]: 4-authentication-permissions-and-throttling.md
[tut-4]: 4-authentication-and-permissions.md

183
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@ -0,0 +1,183 @@
# Tutorial 4: Authentication & Permissions
Currently our API doesn't have any restrictions on who can
## Adding information to our model
We're going to make a couple of changes to our `Snippet` model class.
First, let's add a couple of fields. One of those fields will be used to represent the user who created the code snippet. The other field will be used to store the highlighted HTML representation of the code.
Add the following two fields to the model.
owner = models.ForeignKey('auth.User', related_name='snippets')
highlighted = models.TextField()
We'd also need to make sure that when the model is saved, that we populate the highlighted field, using the `pygments` code higlighting library.
We'll ned some extra imports:
from pygments.lexers import get_lexer_by_name
from pygments.formatters import HtmlFormatter
from pygments import highlight
And now we can add a `.save()` method to our model class:
def save(self, *args, **kwargs):
"""
Use the `pygments` library to create an highlighted HTML
representation of the code snippet.
"""
lexer = get_lexer_by_name(self.language)
linenos = self.linenos and 'table' or False
options = self.title and {'title': self.title} or {}
formatter = HtmlFormatter(style=self.style, linenos=linenos,
full=True, **options)
self.highlighted = highlight(self.code, lexer, formatter)
super(Snippet, self).save(*args, **kwargs)
When that's all done we'll need to update our database tables.
Normally we'd create a database migration in order to do that, but for the purposes of this tutorial, let's just delete the database and start again.
rm tmp.db
python ./manage.py syncdb
You might also want to create a few different users, to use for testing the API. The quickest way to do this will be with the `createsuperuser` command.
python ./manage.py createsuperuser
## Adding endpoints for our User models
Now that we've got some users to work with, we'd better add representations of those users to our API. Creating a new serializer is easy:
class UserSerializer(serializers.ModelSerializer):
snippets = serializers.ManyPrimaryKeyRelatedField()
class Meta:
model = User
fields = ('pk', 'username', 'snippets')
Because `'snippets'` is a *reverse* relationship on the User model, it will not be included by default when using the `ModelSerializer` class, so we've needed to add an explicit field for it.
We'll also add a couple of views. We'd like to just use read-only views for the user representations, so we'll use the `ListAPIView` and `RetrieveAPIView` generic class based views.
class UserList(generics.ListAPIView):
model = User
serializer_class = UserSerializer
class UserInstance(generics.RetrieveAPIView):
model = User
serializer_class = UserSerializer
Finally we need to add those views into the API, by referencing them from the URL conf.
url(r'^users/$', views.UserList.as_view()),
url(r'^users/(?P<pk>[0-9]+)/$', views.UserInstance.as_view())
## Associating Snippets with Users
Right now, if we created a code snippet, there'd be no way of associating the user that created the snippet, with the snippet instance. The user isn't sent as part of the serialized representation, but is instead a property of the incoming request.
The way we deal with that is by overriding a `.pre_save()` method on our snippet views, that allows us to handle any information that is implicit in the incoming request or requested URL.
On **both** the `SnippetList` and `SnippetInstance` view classes, add the following method:
def pre_save(self, obj):
obj.owner = self.request.user
## Updating our serializer
Now that snippets are associated with the user that created them, let's update our SnippetSerializer to reflect that.
Add the following field to the serializer definition:
owner = serializers.Field(source='owner.username')
**Note**: Make sure you also add `'owner',` to the list of fields in the inner `Meta` class.
This field is doing something quite interesting. The `source` argument controls which attribtue is used to populate a field, and can point at any attribute on the serialized instance. It can also take the dotted notation shown above, in which case it will traverse the given attributes, in a similar way as is used with Django's template language.
The field we've added is the untyped `Field` class, in contrast to the other typed fields, such as `CharField`, `BooleanField` etc... The untyped `Field` is always read-only, and will be used for serialized representations, but will not be used for updating model instances when they are deserialized.
## Adding required permissions to views
Now that code snippets are associated with users we want to make sure that only authenticated users are able to create, update and delete code snippets.
REST framework includes a number of permission classes that we can use to restrict who can access a given view. In this case the one we're looking for is `IsAuthenticatedOrReadOnly`, which will ensure that authenticated requests get read-write access, and unauthenticated requests get read-only access.
Add the following property to **both** the `SnippetList` and `SnippetInstance` view classes.
permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
**TODO: Now that the permissions are restricted, demonstrate using HTTP basic authentication with curl requests**
## Adding login to the Browseable API
If you open a browser and navigate to the browseable API at the moment, you'll find you're no longer able to create new code snippets. In order to do so we'd need to be able to login as a user.
We can add a login view for use with the browseable API, by editing our URLconf once more.
Add the following import at the top of the file:
from django.conf.urls import include
And, at the end of the file, add a pattern to include the login and logout views for the browseable API.
urlpatterns += patterns('',
url(r'^api-auth/', include('rest_framework.urls',
namespace='rest_framework'))
)
The `r'^api-auth/'` part of pattern can actually be whatever URL you want to use. The only restriction is that the included urls must use the `'rest_framework'` namespace.
Now if you open up the browser again and refresh the page you'll see a 'Login' link in the top right of the page. If you log in as one of the users you created earier, you'll be able to create code snippets again.
Once you've created a few code snippets, navigate to the '/users/' endpoint, and notice that the representation includes a list of the snippet pks that are associated with each user, in each user's 'snippets' field.
## Object level permissions
Really we'd like all code snippets to be visible to anyone, but also make sure that only the user that created a code snippet is able update or delete it.
To do that we're going to need to create a custom permission.
In the snippets app, create a new file, `permissions.py`
from rest_framework import permissions
class IsOwnerOrReadOnly(permissions.BasePermission):
"""
Custom permission to only allow owners of an object to edit it.
"""
def has_permission(self, request, view, obj=None):
# Skip the check unless this is an object-level test
if obj is None:
return True
# Read permissions are allowed to any request
if request.method in permissions.SAFE_METHODS:
return True
# Write permissions are only allowed to the owner of the snippet
return obj.owner == request.user
Now we can add that custom permission to our snippet instance endpoint, by editing the `permission_classes` property on the `SnippetInstance` class:
permission_classes = (permissions.IsAuthenticatedOrReadOnly,
IsOwnerOrReadOnly,)
Make sure to also import the `IsOwnerOrReadOnly` class.
from snippets.permissions import IsOwnerOrReadOnly
Now, if you open a browser again, you find that the 'DELETE' and 'PUT' actions only appear on a snippet instance endpoint if you're logged in as the same user that created the code snippet.
## Summary
We've now got a fairly fine-grained set of permissions on our Web API, and end points for users of the system and for the code snippets that they have created.
In [part 5][tut-5] of the tutorial we'll look at how we can tie everything together by creating an HTML endpoint for our hightlighted snippets, and improve the cohesion of our API by using hyperlinking for the relationships within the system.
[tut-5]: 5-relationships-and-hyperlinked-apis.md

5
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@ -1,5 +0,0 @@
# Tutorial 4: Authentication & Permissions
Nothing to see here. Onwards to [part 5][tut-5].
[tut-5]: 5-relationships-and-hyperlinked-apis.md

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@ -1,11 +1,157 @@
# Tutorial 5 - Relationships & Hyperlinked APIs
**TODO**
At the moment relationships within our API are represented by using primary keys. In this part of the tutorial we'll improve the cohesion and discoverability of our API, by instead using hyperlinking for relationships.
* Create BlogPost model
* Demonstrate nested relationships
* Demonstrate and describe hyperlinked relationships
## Creating an endpoint for the root of our API
<!-- Onwards to [part 6][tut-6].
Right now we have endpoints for 'snippets' and 'users', but we don't have a single entry point to our API. To create one, we'll use a regular function-based view and the `@api_view` decorator we introduced earlier.
[tut-6]: 6-resource-orientated-projects.md -->
from rest_framework import renderers
from rest_framework.decorators import api_view
from rest_framework.response import Response
from rest_framework.reverse import reverse
@api_view(('GET',))
def api_root(request, format=None):
return Response({
'users': reverse('user-list', request=request),
'snippets': reverse('snippet-list', request=request)
})
Notice that we're using REST framework's `reverse` function in order to return fully-qualified URLs.
## Creating an endpoint for the highlighted snippets
The other obvious thing that's still missing from our pastebin API is the code highlighting endpoints.
Unlike all our other API endpoints, we don't want to use JSON, but instead just present an HTML representation. There are two style of HTML renderer provided by REST framework, one for dealing with HTML rendered using templates, the other for dealing with pre-rendered HTML. The second renderer is the one we'd like to use for this endpoint.
The other thing we need to consider when creating the code highlight view is that there's no existing concreate generic view that we can use. We're not returning an object instance, but instead a property of an object instance.
Instead of using a concrete generic view, we'll use the base class for representing instances, and create our own `.get()` method.
class SnippetHighlight(generics.SingleObjectAPIView):
model = Snippet
renderer_classes = (renderers.StaticHTMLRenderer,)
def get(self, request, *args, **kwargs):
snippet = self.get_object()
return Response(snippet.highlighted)
As usual we need to add the new views that we've created in to our URLconf.
We'll add a url pattern for our new API root:
url(r'^$', 'api_root'),
And then add a url pattern for the snippet highlights:
url(r'^snippets/(?P<pk>[0-9]+)/highlight/$', views.SnippetHighlight.as_view()),
## Hyperlinking our API
Dealing with relationships between entities is one of the more challenging aspects of Web API design. There are a number of different ways that we might choose to represent a relationship:
* Using primary keys.
* Using hyperlinking between entities.
* Using a unique identifying slug field on the related entity.
* Using the default string representation of the related entity.
* Nesting the related entity inside the parent representation.
* Some other custom representation.
REST framework supports all of these styles, and can apply them across forward or reverse relationships, or apply them across custom managers such as generic foreign keys.
In this case we'd like to use a hyperlinked style between entities. In order to do so, we'll modify our serializers to extend `HyperlinkedModelSerializer` instead of the existing `ModelSerializer`.
The `HyperlinkedModelSerializer` has the following differences from `ModelSerializer`:
* It does not include the `pk` field by default.
* It includes a `url` field, using `HyperlinkedIdentityField`.
* Relationships use `HyperlinkedRelatedField` and `ManyHyperlinkedRelatedField`,
instead of `PrimaryKeyRelatedField` and `ManyPrimaryKeyRelatedField`.
We can easily re-write our existing serializers to use hyperlinking.
class SnippetSerializer(serializers.HyperlinkedModelSerializer):
owner = serializers.Field(source='owner.username')
highlight = serializers.HyperlinkedIdentityField(view_name='snippet-highlight')
class Meta:
model = models.Snippet
fields = ('url', 'highlight', 'owner',
'title', 'code', 'linenos', 'language', 'style')
class UserSerializer(serializers.HyperlinkedModelSerializer):
snippets = serializers.ManyHyperlinkedRelatedField(view_name='snippet-detail')
class Meta:
model = User
fields = ('url', 'username', 'snippets')
Notice that we've also added a new `'highlight'` field. This field is of the same type as the `url` field, except that it points to the `'snippet-highlight'` url pattern, instead of the `'snippet-detail'` url pattern.
## Making sure our URL patterns are named
If we're going to have a hyperlinked API, we need to make sure we name our URL patterns. Let's take a look at which URL patterns we need to name.
* The root of our API refers to `'user-list'` and `'snippet-list'`.
* Our snippet serializer includes a field that refers to `'snippet-highlight'`.
* Our user serializer includes a field that refers to `'snippet-detail'`.
* Our snippet and user serializers include `'url'` fields that by default will refer to `'{model_name}-detail'`, which in this case will be `'snippet-detail'` and `'user-detail'`.
After adding all those names into our URLconf, our final `'urls.py'` file should look something like this:
# API endpoints
urlpatterns = format_suffix_patterns(patterns('snippets.views',
url(r'^$', 'api_root'),
url(r'^snippets/$',
views.SnippetList.as_view(),
name='snippet-list'),
url(r'^snippets/(?P<pk>[0-9]+)/$',
views.SnippetInstance.as_view(),
name='snippet-detail'),
url(r'^snippets/(?P<pk>[0-9]+)/highlight/$'
views.SnippetHighlight.as_view(),
name='snippet-highlight'),
url(r'^users/$',
views.UserList.as_view(),
name='user-list'),
url(r'^users/(?P<pk>[0-9]+)/$',
views.UserInstance.as_view(),
name='user-detail')
))
# Login and logout views for the browsable API
urlpatterns += patterns('',
url(r'^api-auth/', include('rest_framework.urls',
namespace='rest_framework'))
)
## Reviewing our work
If we open a browser and navigate to the browseable API, you'll find that you can now work your way around the API simply by following links.
You'll also be able to see the 'highlight' links on the snippet instances, that will take you to the hightlighted code HTML representations.
We've now got a complete pastebin Web API, which is fully web browseable, and comes complete with authentication, per-object permissions, and multiple renderer formats.
We've walked through each step of the design process, and seen how if we need to customize anything we can gradually work our way down to simply using regular Django views.
You can review the final [tutorial code][repo] on GitHub, or try out a live example in [the sandbox][sandbox].
## Onwards and upwards.
We've reached the end of our tutorial. If you want to get more involved in the REST framework project, here's a few places you can start:
* Contribute on [GitHub][github] by reviewing and subitting issues, and making pull requests.
* Join the [REST framework discussion group][group], and help build the community.
* Follow the author [on Twitter][twitter] and say hi.
**Now go build some awesome things.**
[repo]: https://github.com/tomchristie/rest-framework-tutorial
[sandbox]: http://sultry-coast-6726.herokuapp.com/
[github]: https://github.com/tomchristie/django-rest-framework
[group]: https://groups.google.com/forum/?fromgroups#!forum/django-rest-framework
[twitter]: https://twitter.com/_tomchristie