diff options
Diffstat (limited to 'docs/tutorial/1-serialization.md')
| -rw-r--r-- | docs/tutorial/1-serialization.md | 98 |
1 files changed, 69 insertions, 29 deletions
diff --git a/docs/tutorial/1-serialization.md b/docs/tutorial/1-serialization.md index e61fb946..ed54a876 100644 --- a/docs/tutorial/1-serialization.md +++ b/docs/tutorial/1-serialization.md @@ -4,11 +4,11 @@ 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. --> +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. --- -**Note**: The final code for this tutorial is available in the [tomchristie/rest-framework-tutorial][repo] repository on GitHub. There is also a sandbox version for testing, [available here][sandbox]. +**Note**: The code for this tutorial is available in the [tomchristie/rest-framework-tutorial][repo] repository on GitHub. The completed implementation is also online as a sandbox version for testing, [available here][sandbox]. --- @@ -60,7 +60,7 @@ We'll also need to add our new `snippets` app and the `rest_framework` app to `I INSTALLED_APPS = ( ... 'rest_framework', - 'snippets' + 'snippets', ) We also need to wire up the root urlconf, in the `tutorial/urls.py` file, to include our snippet app's URLs. @@ -73,19 +73,20 @@ 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 `Snippet` model that is used to store code snippets. Go ahead and edit the `snippets` 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. Note: Good programming practices include comments. Although you will find them in our repository version of this tutorial code, we have omitted them here to focus on the code itself. from django.db import models 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())) + + LEXERS = [item for item in get_all_lexers() if item[1]] + LANGUAGE_CHOICES = sorted([(item[1][0], item[0]) for item in LEXERS]) + STYLE_CHOICES = sorted((item, item) for item in get_all_styles()) class Snippet(models.Model): created = models.DateTimeField(auto_now_add=True) - title = models.CharField(max_length=100, default='') + title = models.CharField(max_length=100, blank=True, default='') code = models.TextField() linenos = models.BooleanField(default=False) language = models.CharField(choices=LANGUAGE_CHOICES, @@ -108,7 +109,7 @@ The first thing we need to get started on our Web API is provide a way of serial from django.forms import widgets from rest_framework import serializers - from snippets import models + from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES class SnippetSerializer(serializers.Serializer): @@ -118,26 +119,30 @@ The first thing we need to get started on our Web API is provide a way of serial code = serializers.CharField(widget=widgets.Textarea, max_length=100000) linenos = serializers.BooleanField(required=False) - language = serializers.ChoiceField(choices=models.LANGUAGE_CHOICES, + language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default='python') - style = serializers.ChoiceField(choices=models.STYLE_CHOICES, + style = serializers.ChoiceField(choices=STYLE_CHOICES, default='friendly') def restore_object(self, attrs, instance=None): """ - Create or update a new snippet instance. + Create or update a new snippet instance, given a dictionary + of deserialized field values. + + Note that if we don't define this method, then deserializing + data will simply return a dictionary of items. """ if instance: # Update existing instance - instance.title = attrs['title'] - instance.code = attrs['code'] - instance.linenos = attrs['linenos'] - instance.language = attrs['language'] - instance.style = attrs['style'] + instance.title = attrs.get('title', instance.title) + instance.code = attrs.get('code', instance.code) + instance.linenos = attrs.get('linenos', instance.linenos) + instance.language = attrs.get('language', instance.language) + instance.style = attrs.get('style', instance.style) return instance # Create new instance - return models.Snippet(**attrs) + return 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. @@ -149,13 +154,16 @@ Before we go any further we'll familiarize ourselves with using our new Serializ python manage.py shell -Okay, once we've got a few imports out of the way, let's create a code snippet to work with. +Okay, once we've got a few imports out of the way, let's create a couple of code snippets to work with. from snippets.models import Snippet from snippets.serializers import SnippetSerializer from rest_framework.renderers import JSONRenderer from rest_framework.parsers import JSONParser + snippet = Snippet(code='foo = "bar"\n') + snippet.save() + snippet = Snippet(code='print "hello, world"\n') snippet.save() @@ -163,13 +171,13 @@ We've now got a few snippet instances to play with. Let's take a look at serial serializer = SnippetSerializer(snippet) serializer.data - # {'pk': 1, 'title': u'', 'code': u'print "hello, world"\n', 'linenos': False, 'language': u'python', 'style': u'friendly'} + # {'pk': 2, '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 finalize the serialization process we render the data into `json`. content = JSONRenderer().render(serializer.data) content - # '{"pk": 1, "title": "", "code": "print \\"hello, world\\"\\n", "linenos": false, "language": "python", "style": "friendly"}' + # '{"pk": 2, "title": "", "code": "print \\"hello, world\\"\\n", "linenos": false, "language": "python", "style": "friendly"}' Deserialization is similar. First we parse a stream into python native datatypes... @@ -188,9 +196,15 @@ Deserialization is similar. First we parse a stream into python native datatype 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. +We can also serialize querysets instead of model instances. To do so we simply add a `many=True` flag to the serializer arguments. + + serializer = SnippetSerializer(Snippet.objects.all(), many=True) + serializer.data + # [{'pk': 1, 'title': u'', 'code': u'foo = "bar"\n', 'linenos': False, 'language': u'python', 'style': u'friendly'}, {'pk': 2, 'title': u'', 'code': u'print "hello, world"\n', 'linenos': False, 'language': u'python', 'style': u'friendly'}] + ## 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. +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 our 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. @@ -202,8 +216,6 @@ Open the file `snippets/serializers.py` again, and edit the `SnippetSerializer` model = Snippet fields = ('id', '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. @@ -229,7 +241,6 @@ Edit the `snippet/views.py` file, and add the following. kwargs['content_type'] = 'application/json' super(JSONResponse, self).__init__(content, **kwargs) - 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 @@ -239,7 +250,7 @@ The root of our API is going to be a view that supports listing all the existing """ if request.method == 'GET': snippets = Snippet.objects.all() - serializer = SnippetSerializer(snippets) + serializer = SnippetSerializer(snippets, many=True) return JSONResponse(serializer.data) elif request.method == 'POST': @@ -288,16 +299,45 @@ Finally we need to wire these views up. Create the `snippets/urls.py` file: urlpatterns = patterns('snippets.views', url(r'^snippets/$', 'snippet_list'), - url(r'^snippets/(?P<pk>[0-9]+)/$', 'snippet_detail') + url(r'^snippets/(?P<pk>[0-9]+)/$', 'snippet_detail'), ) It's worth noting that there are 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. ## Testing our first attempt at a Web API -**TODO: Describe using runserver and making example requests from console** +Now we can start up a sample server that serves our snippets. + +Quit out of the shell... + + quit() + +...and start up Django's development server. + + python manage.py runserver + + Validating models... + + 0 errors found + Django version 1.4.3, using settings 'tutorial.settings' + Development server is running at http://127.0.0.1:8000/ + Quit the server with CONTROL-C. + +In another terminal window, we can test the server. + +We can get a list of all of the snippets. + + curl http://127.0.0.1:8000/snippets/ + + [{"id": 1, "title": "", "code": "foo = \"bar\"\n", "linenos": false, "language": "python", "style": "friendly"}, {"id": 2, "title": "", "code": "print \"hello, world\"\n", "linenos": false, "language": "python", "style": "friendly"}] + +Or we can get a particular snippet by referencing its id. + + curl http://127.0.0.1:8000/snippets/2/ + + {"id": 2, "title": "", "code": "print \"hello, world\"\n", "linenos": false, "language": "python", "style": "friendly"} -**TODO: Describe opening in a web browser and viewing json output** +Similarly, you can have the same json displayed by visiting these URLs in a web browser. ## Where are we now |