翻譯如下:

教程 2: Requests and Responses

從這個角度我們將真正開始覆蓋其他框架的核心。讓我們介紹幾個基本構建塊。

1. Request Object  ——Request物件

rest framework 引入了一個繼承自HttpRequest的Request物件，該物件提供了對請求的更靈活解析。request物件的核心部分是request.data屬性，類似於request.post, 但在使用WEB API時，request.data更有效。

request.POST  # Only handles form data.  Only works for 'POST' method.
 

request.DATA  # Handles arbitrary data.  Works any HTTP request with content.

rest framework引入了一個Response 物件，它繼承自TemplateResponse物件。它獲得未渲染的內容並通過內容協商content negotiation 來決定正確的content type返回給client。

returnResponse(data)# Renders to content type as requested by the client.
 

在views當中使用數字化的HTTP狀態碼，會使你的程式碼不宜閱讀，且不容易發現程式碼中的錯誤。rest framework為每個狀態碼提供了更明確的標識。例如HTTP_400_BAD_REQUEST。相比於使用數字，在整個views中使用這類識別符號將更好。

4. 封裝API views

在編寫API views時，REST Framework提供了兩種wrappers：

1).  @api_viwe 裝飾器 ——函式級別

2). APIView 類——類級別

這兩種封裝器提供了許多功能，例如，確保在view當中能夠接收到Request例項；往Response中增加內容以便內容協商content negotiation 

封裝器也提供一些行為，例如在適當的時候返回405 Methord Not Allowed響應；在訪問多型別的輸入request.DATA時，處理任何的ParseError異常。

5. 彙總

我們開始用這些新的元件來寫一些views。

我們不在需要JESONResponse 類（在前一篇中建立），將它刪除。刪除後我們開始稍微重構下我們的view

from rest_framework import status
from rest_framework.decorators import api_view
from rest_framework.response importResponsefrom snippets.models importSnippetfrom snippets.serializers importSnippetSerializer@api_view(['GET','POST'])def snippet_list(request):"""
    List all snippets, or create a new snippet.
    """if request.method =='GET':
        snippets =Snippet.objects.all()
        serializer =SnippetSerializer(snippets)returnResponse(serializer.data)elif request.method =='POST':
        serializer =SnippetSerializer(data=request.DATA)if serializer.is_valid():
            serializer.save()returnResponse(serializer.data, status=status.HTTP_201_CREATED)else:returnResponse(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

下面是對單個snippet操作的view更新：

@api_view(['GET','PUT','DELETE'])def snippet_detail(request, pk):"""
    Retrieve, update or delete a snippet instance.
    """try:
        snippet =Snippet.objects.get(pk=pk)exceptSnippet.DoesNotExist:returnResponse(status=status.HTTP_404_NOT_FOUND)if request.method =='GET':
        serializer =SnippetSerializer(snippet)returnResponse(serializer.data)elif request.method =='PUT':
        serializer =SnippetSerializer(snippet, data=request.DATA)if serializer.is_valid():
            serializer.save()returnResponse(serializer.data)else:returnResponse(serializer.errors, status=status.HTTP_400_BAD_REQUEST)elif request.method =='DELETE':
        snippet.delete()returnResponse(status=status.HTTP_204_NO_CONTENT)

6. 給URLs增加可選的格式字尾

利用在response時不需要指定content type這一事實，我們在API端增加格式的字尾。使用格式字尾，可以明確的指出使用某種格式，意味著我們的API可以處理類似http://example.com/api/items/4.json.的URL。

增加format引數在views中，如：

def snippet_list(request, format=None):

and

def snippet_detail(request, pk, format=None):

from django.conf.urls import patterns, url
from rest_framework.urlpatterns import format_suffix_patterns

urlpatterns = patterns('snippets.views',
    url(r'^snippets/$','snippet_list'),
    url(r'^snippets/(?P<pk>[0-9]+)$','snippet_detail'),)

urlpatterns = format_suffix_patterns(urlpatterns)

這些額外的url patterns並不是必須的。

Browsability

Because the API chooses the content type of the response based on the client request, it will, by default, return an HTML-formatted representation of the resource when that resource is requested by a web browser. This allows for the API to return a fully web-browsable HTML representation.

Having a web-browsable API is a huge usability win, and makes developing and using your API much easier. It also dramatically lowers the barrier-to-entry for other developers wanting to inspect and work with your API.

See the browsable api topic for more information about the browsable API feature and how to customize it.

What's next?

In tutorial part 3, we'll start using class based views, and see how generic views reduce the amount of code we need to write.