本节内容
| 一 Class Based View 基于类的视图 |
function view 存在问题，无法继承复用，尤其时框架封装好的类用不了，function组装复用更擅长
class based view 代码更简洁
简单样例
version 1
# urls.py
from django.conf.urls import url
from mysite import views as my_view urlpatterns = [
url(r'^about/', my_view.about),
] # mysite/views.py
from django.shortcuts import render def about(request):
return render(request, 'about.html')
基本的function based view
version 2
# urls.py
from django.views.generic import TemplateView
urlpatterns = [
url(r'^about/', TemplateView.as_view(template_name='about.html')),
] # mysite/views.py
from django.shortcuts import render def about(request):
return render(request, 'about.html')
TemplateView.as_view(template_name='about.html')) 方法 as_view()，参数template_name=‘网页模板’
version 3
# mysite/views.py
from django.views.generic import TemplateView
class AboutView(TemplateView):
template_name = 'about.html' #mysite/urls.py
from mysite import views as my_view urlpatterns = [
url(r'^about/', my_view.AboutView.as_view()),
]
说明：
as_view()返回的是一个function object
模板名字作为as_view参数传进去，也可以作为类变量设置template_name = '网页模板'
1. 类的视图 View
# mysite/views.py
def my_view(request):
if request.method == 'GET':
return render(request, 'about.html')
elif request.method == 'POST':
return HttpResponse('post it')
elif request.method == 'HEAD':
return HttpResponse('head it')
# mysite/urls.py
from mysite import views
urlpatterns = [
url(r'^about/', views.my_view),
]
等价于 类图公共基类View
# mysite/views.py
from django.shortcuts import render,HttpResponse
from django.views.generic import View class MyView(View):
def get(self, request):
return render(request, 'about.html') def post(self, request):
return HttpResponse('post it') def head(self, request):
return HttpResponse('head it') # mysite/urls.py
from mysite import views as my_view
urlpatterns = [
url(r'^about/', my_view.MyView.as_view()),
]
类视图好处就是可以直接继承和覆盖
# mysite/views.py
from django.views.generic import View
class GreetingView(View):
greeting = 'Good Day'
def get(self, request):
return HttpResponse(self.greeting) class MorningGreeting(GreetingView):
greeting = 'Morning to ya' # mysite/urls.py
urlpatterns = [
my_view.GreetingView.as_view(greeting="G'day")),
]
源码分析
class View(object):
# 所有views的公共类，仅仅实现 dispatch方法和简单安全性验证 http_method_names = ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace'] def __init__(self, **kwargs):
for key, value in six.iteritems(kwargs):
setattr(self, key, value) @classonlymethod
def as_view(cls, **initkwargs):
# request-response的主入口点 for key in initkwargs:
# 不能有get,post等方法名的参数，后续有setattr()操作，会覆盖原始请求方法
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__)) # 如果传入了一个没有定义的类属性，就报错；如有greeting属性，就不报错
if not hasattr(cls, key):
raise TypeError("%s() received an invalid keyword %r. as_view "
"only accepts arguments that are already "
"attributes of the class." % (cls.__name__, key)) # 定义了类似闭包的视图函数
def view(request, *args, **kwargs):
self = cls(**initkwargs) # 调用__init__()进行实例化
if hasattr(self, 'get') and not hasattr(self, 'head'):
self.head = self.get
self.request = request
self.args = args
self.kwargs = kwargs
return self.dispatch(request, *args, **kwargs) # 调用 self.dispatch()进行处理 # 对view object设置了一些属性
view.view_class = cls
view.view_initkwargs = initkwargs # 更新文档说明
update_wrapper(view, cls, updated=()) # and possible attributes set by decorators
# like csrf_exempt from dispatch
update_wrapper(view, cls.dispatch, assigned=())
return view def dispatch(self, request, *args, **kwargs):
# 将request.method反射到类相应的方法上，并执行
if request.method.lower() in self.http_method_names:
# 如果有如get，就handler=get；如果没有handler = self.http_method_not_allowed
handler = getattr(self, request.method.lower(), self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
return handler(request, *args, **kwargs) def http_method_not_allowed(self, request, *args, **kwargs):
logger.warning(
'Method Not Allowed (%s): %s', request.method, request.path,
extra={'status_code': 405, 'request': request}
)
return http.HttpResponseNotAllowed(self._allowed_methods()) def options(self, request, *args, **kwargs):
"""
Handles responding to requests for the OPTIONS HTTP verb.
"""
response = http.HttpResponse()
response['Allow'] = ', '.join(self._allowed_methods())
response['Content-Length'] = ''
return response def _allowed_methods(self):
return [m.upper() for m in self.http_method_names if hasattr(self, m)]
类View
#!/usr/bin/env python3
# -*-coding:utf-8 -*-
# __author__:Jonathan
# email:nining1314@gmail.com from django.shortcuts import HttpResponse
from django import http
from django.utils import six
from django.utils.decorators import classonlymethod
from django.conf.urls import url class View(object):
http_method_names = ['get', 'post', 'put', 'patch', 'delete', 'head', 'options', 'trace'] def __init__(self, **kwargs):
for key, value in six.iteritems(kwargs):
setattr(self, key, value) @classonlymethod
def as_view(cls, **initkwargs):
for key in initkwargs:
if key in cls.http_method_names:
raise TypeError("禁止 %s 作为 %s()关键字参数" % (key, cls.__name__))
if not hasattr(cls, key):
raise TypeError("类 %s() 接收到非法参数 %s，只接受类存在类属性" % (cls.__name__, key)) def view(request, *args, **kwargs):
# 把 as_view()传入的关键字参数，赋值为相应的类变量
self = cls(**initkwargs) # 类的实例化，虽然只是一行代码，要理解原理：是有很多行代码执行完的结果
if hasattr(self, 'get') and not hasattr(self, 'head'):
self.head = self.get
self.request = request
self.args = args
self.kwargs = kwargs
return self.dispatch(request, *args, **kwargs) # 一行代码，代表的是self.dispatch()的执行结果 # 函数也是一种对象，可以有自己的属性****
view.view_class = cls
view.view_initkwargs = initkwargs # 返回闭合的函数对象
return view def dispatch(self, request, *args, **kwargs):
if request.method.lower() in self.http_method_names:
handler = getattr(self, request.method.lower(), self.http_method_not_allowed)
else:
handler = self.http_method_not_allowed
return handler(request, *args, **kwargs) # 一行代码，代表的是handler()的执行结果
"""最终dispatch结果：根据request.method.lower()得到相应的http请求方法，反射到同名类方法，执行""" def http_method_not_allowed(self, request, *args, **kwargs):
return http.HttpResponseNotAllowed(self._allowed_methods()) def _allowed_methods(self):
return [m.upper() for m in self.http_method_names if hasattr(self, m)] class MyView(View):
def get(self, request):
return HttpResponse('get it') def post(self, request):
return HttpResponse('post it') def head(self, request):
return HttpResponse('head it') urlpatterns = [
url(r'^my_view/', MyView.as_view()),
]
吃透类View
说明：
as_view返回一个 view function
as_view接收参数是可以覆盖类定义的变量
__init__检查as_view传入的参数是否在类中定义
View.as_view()返回函数视图的view 对象，说明类视图只是对原有的函数视图进行了封装，而没有否定函数view的作用
view function运行时会调用dispatch，根据用户的request.method路由到get, post等方法
最终得出结论：
View类 在没有更改原Django逻辑的情况下，可以用类来编写view，每个http请求会使用对应类的同名方法进行处理
2. 类的视图 TemplateView
class ContextMixin(object):
# 渲染模板时，处理需要的上下文参数 def get_context_data(self, **kwargs):
if 'view' not in kwargs:
kwargs['view'] = self
return kwargs class TemplateResponseMixin(object):
# 渲染模板，Mixin一般是小功能类封装，被其他类继承 template_name = None
template_engine = None
response_class = TemplateResponse
content_type = None def render_to_response(self, context, **response_kwargs):
# 进行模板渲染，render()是个函数，response_class()是个类，实现本质目标没多大区别 response_kwargs.setdefault('content_type', self.content_type)
return self.response_class(
request=self.request,
template=self.get_template_names(),
context=context,
using=self.template_engine,
**response_kwargs
) def get_template_names(self):
if self.template_name is None:
raise ImproperlyConfigured(
"TemplateResponseMixin requires either a definition of "
"'template_name' or an implementation of 'get_template_names()'")
else:
return [self.template_name] class TemplateView(TemplateResponseMixin, ContextMixin, View):
# 实现get()方法，有渲染上文参数，有渲染操作 def get(self, request, *args, **kwargs):
context = self.get_context_data(**kwargs)
return self.render_to_response(context)
类TemplateView
说明：
每个Mixin只提供部分功能，最终需要类整合
TemplateResponseMixin提供render_to_response() 方法，渲染模板
ContentMixin提供get_context_data()方法，提供渲染数据
View提供get，post用户访问接口
- 面向对象编程：如何拆分功能模块，如何组装功能模块
3. 类的视图 login_required解决方法
3.1 封装Mixin(推荐)
from django.contrib.auth.decorators import login_required class LoginRequiredMixin(object):
@classmethod
def as_view(cls, **initkwargs):
view = super(LoginRequiredMixin, cls).as_view(**initkwargs)
return login_required(view) class MyView(LoginRequiredMixin, ...):
pass
3.2 装饰类
from django.contrib.auth.decorators import login_required
from django.utils.decorators import method_decorator
from django.views.generic import TemplateView class ProtectedView(TemplateView):
template_name = 'secret.html' @method_decorator(login_required)
def dispatch(self, request, *args, **kwargs):
return super(ProtectedView, self).dispatch(*args, **kwargs)
推荐学习网站：http://devdocs.io/
| 二 通用视图 |
通用视图(generic class base view) 和 class base view 概念上不是一回事
Class Base View 是指用类的方式去写视图
通用视图 是用Class Base View的方式将我们常用的增、删、改、查封装成可扩展的类，使用时直接继承、快速实现
1. 通用视图 - ListView
配置编程，获取数据列表
from django.db import models class Publisher(models.Model):
name = models.CharField(max_length=30)
address = models.CharField(max_length=50)
city = models.CharField(max_length=60)
state_province = models.CharField(max_length=30)
country = models.CharField(max_length=50)
website = models.URLField() def __str__(self):
return self.name class Author(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=40)
email = models.EmailField() def __str__(self):
return '%s %s' % (self.first_name, self.last_name) class Book(models.Model):
title = models.CharField(max_length=100)
authors = models.ManyToManyField('Author')
publisher = models.ForeignKey('Publisher')
publication_date = models.DateField(auto_now_add=True) def __str__(self):
return self.title
models.py
from django.views.generic import ListView
from .models import Publisher class PublisherList(ListView):
model = Publisher # 类属性：指定解析的model
# queryset = Publisher.objects.all()[0:1] # 和model二选一，获取指定数据
context_object_name = 'publishers' # 默认object_list，前端渲染时的上下文参数
# template_name = 'books/publisher_list.html' # 指定渲染的模板文件，默认值model名小写_list.html # 联系类的queryset，而该方法为实例的定制
def get_queryset(self):
print(self.request) # 根据 self.request进行判断，返回符合条件的queryset
return Publisher.objects.all()[0:1]
urlpatterns = [
url(r'^publishers/$', views.PublisherList.as_view(), name='publishers'),
]
说明：
multi object list view
model、queryset和get_queryset三者之间关系
content_object_name
template_name
源码UML图分析：
2. 通用视图 - DetailView
显示一个object的详情页面
from django.views.generic import DetailView
from .models import Publisher
from .models import Book class PublisherDetail(DetailView):
model = Publisher
context_object_name = 'publisher' # 模板渲染对象，默认值object def get_context_data(self, **kwargs):
context = super(PublisherDetail, self).get_context_data(**kwargs)
context['book_list'] = Book.objects.all() # 附加额外选软数据
return context '''
# 默认的object，是从url里的pk获取的
def get_object(self, queryset=None):
object = super(PublisherDetail, self).get_object()
# 进行更新操作
# object.last_accessed = timezone.now()
# object.save()
return object
'''
urlpatterns = [
url(r'^publisher/(?P<pk>[0-9]+)/$', views.PublisherDetail.as_view(), name='publisher-detail'),
]
说明：
Single object detail view
get_context_data
content_object_name
get_object
源码UML图分析：
3. 通用视图 - FormView
FormView
CreateView，UpdateView，DeleteView