一、视图组件的使用
在我们自己书写视图类时需要不断书写重复冗余的代码，看起来十分繁琐不简洁易见，当然rest_framework中的视图组件帮我们做到了一些必要的步骤，使我们节省了编写冗余代码的时间。
1.视图组件的导入
from rest_framework import generics # generics.GenericAPIView 里面封装了APIView
from rest_framework.mixins import (
ListModelMixin, # ListModelMixin表示get请求,获取全部数据
CreateModelMixin, # CreateModelMixin表示post请求，添加数据
DestroyModelMixin, # DestroyModelMixin表示delete请求,删除数据
UpdateModelMixin, # UpdataModelMixin表示put请求，修改数据
RetrieveModelMixin # RetrieveModelMixin表示get请求，获取单条数据
)
2.视图组件的使用
# 视图组件优化第一版
class BookListView(ListModelMixin, CreateModelMixin, generics.GenericAPIView):
'''
使用组件的步骤:
1.获取queryset对象
2.绑定序列化类
'''
queryset = Book.objects.all()
serializer_class = BookSerializer def get(self, request, *args, **kwargs):
return self.list(request, *args, **kwargs) def post(self, request, *args, **kwargs):
return self.create(request, *args, **kwargs)class BookFilterView(RetrieveModelMixin, DestroyModelMixin, UpdateModelMixin, generics.GenericAPIView):
queryset = Book.objects.all()
serializer_class = BookSerializer def get(self, request, *args, **kwargs):
# print(self.kwargs) {'pk': '1'}
return self.retrieve(request, *args, **kwargs) def delete(self, request, *args, **kwargs):
return self.destroy(request, *args, **kwargs) def put(self, request, *args, **kwargs):
return self.update(request, *args, **kwargs)
是不是觉得视图组件帮我们做到了很多麻烦的事，还没完下面是改进版，
# 第二版本
class BookView(generics.ListCreateAPIView):
queryset = Book.objects.all()
serializer_class = BookSerializerclass BookFilterView(generics.RetrieveUpdateDestroyAPIView):
queryset = Book.objects.all()
serializer_class = BookSerializer
不用我们自己写每个请求的方法了，去看看源码：其实是源码帮我们写了 我们要写的了。
class ListCreateAPIView(mixins.ListModelMixin,
mixins.CreateModelMixin,
GenericAPIView):
"""
Concrete view for listing a queryset or creating a model instance.
"""
def get(self, request, *args, **kwargs):
return self.list(request, *args, **kwargs) def post(self, request, *args, **kwargs):
return self.create(request, *args, **kwargs)class RetrieveUpdateAPIView(mixins.RetrieveModelMixin,
mixins.UpdateModelMixin,
GenericAPIView):
"""
Concrete view for retrieving, updating a model instance.
"""
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 patch(self, request, *args, **kwargs):
return self.partial_update(request, *args, **kwargs)
但是，我们还是要写两个这个：
queryset = Book.objects.all()
serializer_class = BookSerializer
最终版本:
在使用时需要注意url中需要对每个请求类型声明
url:
re_path(r'book/$', views.BookView.as_view({
'get': 'list',
'post': 'create'
})),
re_path(r'book/(?P<pk>\d+)/$', views.BookView.as_view({
'get': 'retrieve',
'put': 'update',
'delete': 'destroy'
}))
# 注:在使用ModelViewSet时需要在as_view()中声明请求对应的视图方法，如:get请求对应list ( ListModelMixin )
]
导入与使用:
from rest_framework.viewsets import ModelViewSet #ModelViewSet 里面既封装了mixins又封装了generics中的方法
# 终极版
class BookView(ModelViewSet):
queryset = Book.objects.all()
serializer_class = BookSerializer
只需要导入ModelViewSet就可以解决我们麻烦的冗余代码，看看源码怎么帮我们解决的:
第一步： ModelViewSet类， 继承了放有具体执行每种操作的类(list, create, update, destroy, retrieve)
class ModelViewSet(mixins.CreateModelMixin,
mixins.RetrieveModelMixin,
mixins.UpdateModelMixin,
mixins.DestroyModelMixin,
mixins.ListModelMixin,
GenericViewSet):
"""
A viewset that provides default `create()`, `retrieve()`, `update()`,
`partial_update()`, `destroy()` and `list()` actions.
"""
pass
第二步：GenericViewSet， 这个类啥都没看，继续看父类
class GenericViewSet(ViewSetMixin, generics.GenericAPIView):
"""
The GenericViewSet class does not provide any actions by default,
but does include the base set of generic view behavior, such as
the `get_object` and `get_queryset` methods.
"""
pass
第三步： ViewSetMixin
class ViewSetMixin(object):
"""
This is the magic. Overrides `.as_view()` so that it takes an `actions` keyword that performs
the binding of HTTP methods to actions on the Resource. For example, to create a concrete view binding the 'GET' and 'POST' methods
to the 'list' and 'create' actions... view = MyViewSet.as_view({'get': 'list', 'post': 'create'})
""" @classonlymethod
def as_view(cls, actions=None, **initkwargs):
"""
Because of the way class based views create a closure around the
instantiated view, we need to totally reimplement `.as_view`,
and slightly modify the view function that is created and returned.
"""
# The suffix initkwarg is reserved for displaying the viewset type.
# eg. 'List' or 'Instance'.
cls.suffix = None # The detail initkwarg is reserved for introspecting the viewset type.
cls.detail = None # Setting a basename allows a view to reverse its action urls. This
# value is provided by the router through the initkwargs.
cls.basename = None # actions must not be empty
if not actions:
raise TypeError("The `actions` argument must be provided when "
"calling `.as_view()` on a ViewSet. For example "
"`.as_view({'get': 'list'})`") # sanitize keyword arguments
for key in initkwargs:
if key in cls.http_method_names:
raise TypeError("You tried to pass in the %s method name as a "
"keyword argument to %s(). Don't do that."
% (key, cls.__name__))
if not hasattr(cls, key):
raise TypeError("%s() received an invalid keyword %r" % (
cls.__name__, key)) def view(request, *args, **kwargs):
self = cls(**initkwargs)
# We also store the mapping of request methods to actions,
# so that we can later set the action attribute.
# eg. `self.action = 'list'` on an incoming GET request.
self.action_map = actions # Bind methods to actions
# This is the bit that's different to a standard view
for method, action in actions.items(): # actions ---> {"get": "list", "post": "create"} {"put": "update", "delete": "destroy", "get": "retrieve"}
handler = getattr(self, action) # 第一种get请求 self.list = getattr(self, list) 第二种 get请求 self.retrieve = getattr(self, retrieve)
setattr(self, method, handler) # 第一种get请求 self.get = self.list 第二种get请求 self.get = self.retrieve if hasattr(self, 'get') and not hasattr(self, 'head'):
self.head = self.get self.request = request
self.args = args
self.kwargs = kwargs # And continue as usual
return self.dispatch(request, *args, **kwargs) # take name and docstring from class
update_wrapper(view, cls, updated=()) # and possible attributes set by decorators
# like csrf_exempt from dispatch
update_wrapper(view, cls.dispatch, assigned=()) # We need to set these on the view function, so that breadcrumb
# generation can pick out these bits of information from a
# resolved URL.
view.cls = cls
view.initkwargs = initkwargs
view.suffix = initkwargs.get('suffix', None)
view.actions = actions
return csrf_exempt(view)
这个类里面有as_view(cls, actions=None, **initkwargs)方法， 也就是我们的url里面写的as_view({“get”: “list”, “post”: “create”}),执行的是这个类中的as_view()方法，而不是APIView种的as_view()方法了！
把那个参数字典传给actions,在放回的view函数中，把每种请求要执行的那种方法 setattr()设置了（看代码中注释）；
然后当用户来访问时，执行那个view函数，正常执行dispatch()方法，根据请求方式分发到每种请求的方法中，这次这个方法，是使用setattr()方法设置给self的，没有具体写，也就能正常执行每种方法了。
