Django Class Based View

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本节内容

一 Class Based View 基于类的视图

1. 类的视图 View

2. 类的视图 TemplateView

3. 类的视图 login_required解决方法

二通用视图

1. 通用视图 - ListView

2. 通用视图 - DetailView

3. 通用视图 - FormView

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

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