01 REST框架原始写法，与表单Form类似，实例

1. 创建模型(models.py)

from django.db import models
# 高亮文本， 两种风格
from pygments.lexers import get_all_lexers
from pygments.styles import 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, blank=True, 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',)

2. 创建自定义的Serializer类（serializers.py）

from rest_framework import serializers
from snippets.models import Snippet, LANGUAGE_CHOICES, STYLE_CHOICES

class SnippetSerializer(serializers.Serializer):
# read_only 只读
id = serializers.IntegerField(read_only=True)
# required：必要， allow_blank:允许为空，
title = serializers.CharField(required=False, allow_blank=True, max_length=100)
# style: 设置显示样式，控制如何显示可浏览的API
code = serializers.CharField(style={'base_template': 'textarea.html'})
linenos = serializers.BooleanField(required=False)
language = serializers.ChoiceField(choices=LANGUAGE_CHOICES, default='python')
style = serializers.ChoiceField(choices=STYLE_CHOICES, default='friendly')
# 一般是与model一一对应的，一般可以少，但不可以多，如果想增加需要另外进行处理！
# 字段设置是为了验证前端通过get等方法传递过来的数据
def create(self, validated_data):
"""
根据传入的数据创建一个实例
"""
return Snippet.objects.create(**validated_data)

def update(self, instance, validated_data):
"""
更新一个实例，若没有传值，就使用原来的数据
"""
instance.title = validated_data.get('title', instance.title)
instance.code = validated_data.get('code', instance.code)
instance.linenos = validated_data.get('linenos', instance.linenos)
instance.language = validated_data.get('language', instance.language)
instance.style = validated_data.get('style', instance.style)
instance.save()
return instance

3. 序列化与反序列化

from rest_framework.renderers import JSONRenderer
from rest_framework.parsers import JSONParser
# 序列化，将数据转化成json格式
serializer = SnippetSerializer(snippet)
content = JSONRenderer().render(serializer.data)
# 反序列化，转换成本机类型
from django.utils.six import BytesIO
stream = BytesIO(content)
# 首先将数据转化成二进制流，然后再将其渲染成python中的字典
data = JSONParser().parse(stream)

4. 简便的ModelSerializer，要求不高的数据，不用自定义

class SnippetSerializer(serializers.ModelSerializer):
class Meta:
model = Snippet
fields = ('id', 'title', 'code', 'linenos', 'language', 'style')
# 默认实现了create()和 update()方法

5.重点，编写我们的视图处理函数（views.py）

from django.http import HttpResponse, JsonResponse
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

# 不用进行csrf验证
@csrf_exempt
def snippet_list(request):
# 删除多个对象的方法
if request.method == 'GET':
# 获取所有的对象
snippets = Snippet.objects.all()
# 序列化所有的查询集，必须设置many=True，模型对象不用设置
serializer = SnippetSerializer(snippets, many=True)
return JsonResponse(serializer.data, safe=False)

elif request.method == 'POST':
data = JSONParser().parse(request)
serializer = SnippetSerializer(data=data)
# 验证我们的数据
if serializer.is_valid():
serializer.save()
return JsonResponse(serializer.data, status=201)
return JsonResponse(serializer.errors, status=400)

# 处理单个对象的方法（get, put, delete）
@csrf_exempt
def snippet_detail(request, pk):
"""
Retrieve, update or delete a code snippet.
"""
try:
snippet = Snippet.objects.get(pk=pk)
except Snippet.DoesNotExist:
return HttpResponse(status=404)

if request.method == 'GET':
# 序列化数据
serializer = SnippetSerializer(snippet)
# 将数据转换成json格式，作为响应返回给客户端
return JsonResponse(serializer.data)

elif request.method == 'PUT':
# 将请求对象反序列化为python对象
data = JSONParser().parse(request)
serializer = SnippetSerializer(snippet, data=data)
if serializer.is_valid():
serializer.save()
return JsonResponse(serializer.data)
return JsonResponse(serializer.errors, status=400)

elif request.method == 'DELETE':
snippet.delete()
return HttpResponse(status=204)

6. serializer支持的字段

models.AutoField: IntegerField,
models.BigIntegerField: IntegerField,
models.BooleanField: BooleanField,
models.CharField: CharField,
models.CommaSeparatedIntegerField: CharField,
models.DateField: DateField,
models.DateTimeField: DateTimeField,
models.DecimalField: DecimalField,
models.EmailField: EmailField,
models.Field: ModelField,
models.FileField: FileField,
models.FloatField: FloatField,
models.ImageField: ImageField,
models.IntegerField: IntegerField,
models.NullBooleanField: NullBooleanField,
models.PositiveIntegerField: IntegerField,
models.PositiveSmallIntegerField: IntegerField,
models.SlugField: SlugField,
models.SmallIntegerField: IntegerField,
models.TextField: CharField,
models.TimeField: TimeField,
models.URLField: URLField,
models.GenericIPAddressField: IPAddressField,
models.FilePathField: FilePathField,

7. 自定义字段，支持的参数

LIST_SERIALIZER_KWARGS = (
'read_only', 'write_only', 'required', 'default', 'initial', 'source',
'label', 'help_text', 'style', 'error_messages', 'allow_empty',
'instance', 'data', 'partial', 'context', 'allow_null')