13：基于类的通用视图

骑猪看日落 2023-06-04 05:50 12阅读 0赞

# 基于类的通用视图 #

前面我们说过了django的通用视图，不知道django通用视图的去看我前面的随笔，谢谢

django的通用视图帮我们省略了很多代码，但有时候django的通用视图并不能满足我们全部的需求，例如像重定义一些属性和方法的时候，或者我们想换种写法的时候，因此，django提供了基于类的通用视图，通过子类或者在url中传参的方法来配置我们的基于类的通用视图

通用视图和基于类的通用视图是两种不一样的写法，前面我们介绍的通用视图，所有的代码集中于url的配置文件中，而基于类的通用视图主要集中于配置“继承然后覆盖父类方法和属性”方面，下面是一个基于函数的视图和基于类的视图的对应关系

<table> 
 <thead> 
  <tr> 
   <th>基于函数</th> 
   <th>基于类</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>django.views.generic.simple.direct_to_template</td> 
   <td><a title="django.views.generic.base.TemplateView" rel="nofollow"><span>django.views.generic.base.TemplateView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.simple.redirect_to</td> 
   <td><a title="django.views.generic.base.RedirectView" rel="nofollow"><span>django.views.generic.base.RedirectView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.list_detail.object_list</td> 
   <td><a title="django.views.generic.list.ListView" rel="nofollow"><span>django.views.generic.list.ListView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.list_detail.object_detail</td> 
   <td><a title="django.views.generic.detail.DetailView" rel="nofollow"><span>django.views.generic.detail.DetailView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.create_update.create_object</td> 
   <td><a title="django.views.generic.edit.CreateView" rel="nofollow"><span>django.views.generic.edit.CreateView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.create_update.update_object</td> 
   <td><a title="django.views.generic.edit.UpdateView" rel="nofollow"><span>django.views.generic.edit.UpdateView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.create_update.delete_object</td> 
   <td><a title="django.views.generic.edit.DeleteView" rel="nofollow"><span>django.views.generic.edit.DeleteView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.date_based.archive_index</td> 
   <td><a title="django.views.generic.dates.ArchiveIndexView" rel="nofollow"><span>django.views.generic.dates.ArchiveIndexView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.date_based.archive_year</td> 
   <td><a title="django.views.generic.dates.YearArchiveView" rel="nofollow"><span>django.views.generic.dates.YearArchiveView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.date_based.archive_month</td> 
   <td><a title="django.views.generic.dates.MonthArchiveView" rel="nofollow"><span>django.views.generic.dates.MonthArchiveView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.date_based.archive_week</td> 
   <td><a title="django.views.generic.dates.WeekArchiveView" rel="nofollow"><span>django.views.generic.dates.WeekArchiveView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.date_based.archive_day</td> 
   <td><a title="django.views.generic.dates.DayArchiveView" rel="nofollow"><span>django.views.generic.dates.DayArchiveView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.date_based.archive_today</td> 
   <td><a title="django.views.generic.dates.TodayArchiveView" rel="nofollow"><span>django.views.generic.dates.TodayArchiveView</span></a></td> 
  </tr> 
  <tr> 
   <td>django.views.generic.date_based.object_detail</td> 
   <td><a title="django.views.generic.dates.DateDetailView" rel="nofollow"><span>django.views.generic.dates.DateDetailView</span></a></td> 
  </tr> 
 </tbody> 
</table>

## 简单用法 ##

考虑你仅仅想要显示一个模板about.html，django提供了一个通用视图去做这件事，我们只需要继承它，然后覆盖覆盖模板名称即可，其实TemplateView类对应的是direct\_to\_template

# some_app/views.py
    from django.views.generic import TemplateView
    class AboutView(TemplateView):
        template_name = "about.html"

然后再url配置文件中直接调用相应的方法即可

# urls.py
    from django.conf.urls import patterns, url, include
    from some_app.views import AboutView
    urlpatterns = patterns('',
        (r'^about/', AboutView.as_view()),
    )

或者我们可以直接在url中通过传参的方法达到修改属性的目的

from django.conf.urls import patterns, url, include
    from django.views.generic import TemplateView
    urlpatterns = patterns('',
        (r'^about/', TemplateView.as_view(template_name="about.html")),
    )

## 对象的通用视图 ##

首先这是我们可能会用到的model

# models.py
    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()
        class Meta:
            ordering = ["-name"]
        def __unicode__(self):
            return self.name
    class Book(models.Model):
        title = models.CharField(max_length=100)
        authors = models.ManyToManyField('Author')
        publisher = models.ForeignKey(Publisher)
        publication_date = models.DateField()

为了生成一个所有出版商的页面，我们可以在url中这样写

from django.conf.urls import patterns, url, include
    from django.views.generic import ListView
    from books.models import Publisher
    urlpatterns = patterns('',
        (r'^publishers/$', ListView.as_view(
            model=Publisher,
        )),
    )

在这里我们没有指定模板名，那么会使用ListView默认的模板名默认模板<app\_label>/<model\_name>\_list.html ，这里可能是/books/publisher\_list.html

## 拓展通用视图 ##

### 制作友好的模板上下文名称 ###

如果你在和模型打交道，使用下面的配置可以使你自己定义一个更好用（django内部有规则生成一个）的模板上下文名称，这可能使得和你合作的模板设计师对你有好感，因为有时候django自动生成的模板上下文名称很冗长

urlpatterns = patterns('',
        (r'^publishers/$', ListView.as_view(
            model=Publisher,
            context_object_name="publisher_list",
        )),
    )

### 增加额外的上下文内容 ###

有时候默认的通用视图提供的上下文内容不能满足你的需求，比如一个返回所有出版商的列表的页面，上面可能一点和书籍的信息都没有，这时候你可以通过继承相应的父类，覆盖父类的方法为子类添加额外的内容

from django.views.generic import DetailView
    from books.models import Publisher, Book
    class PublisherDetailView(DetailView):
        context_object_name = "publisher"
        model = Publisher
        def get_context_data(self, **kwargs):
            # Call the base implementation first to get a context
            context = super(PublisherDetailView, self).get_context_data(**kwargs)
            # Add in a QuerySet of all the books
            context['book_list'] = Book.objects.all()
            return context

### 对象的查看子集 ###

注意到的一点，model属性和queryset属性，model=Publisher和queryset=Publisher.objects.all()基本是一致的，基于这一点，我们可以通过制定queryset的方法以至于不必每次都收返回一个模型的全集，可以每次只返回一个子集，当然，我们也可以在url中达到这个目标

urlpatterns = patterns('',
        (r'^publishers/$', ListView.as_view(
            queryset=Publisher.objects.all(),
            context_object_name="publisher_list",
        )),
        (r'^books/$', ListView.as_view(
            queryset=Book.objects.order_by("-publication_date"),
            context_object_name="book_list",
        )),
    )

from django.views.generic import ListView
    from books.models import Book
    class AcmeBookListView(ListView):
        context_object_name = "book_list"
        queryset = Book.objects.filter(publisher__name="Acme Publishing")
        template_name = "books/acme_list.html"

### 动态筛选 ###

还有一个常用的需求是根据url中的参数去查询数据库，之前我们可以把出版商的名字硬编码在url中，但如果我们要写一个能够根据任意给定的出版商，返回该出版商的所有书籍的视图呢？我们可以覆盖get\_queryset()这个方法

def get_queryset(self):
            publisher = get_object_or_404(Publisher, name__iexact=self.args[0])
            return Book.objects.filter(publisher=publisher)

### 执行额外的工作 ###

假如Author这个模型有一个last\_accessed的date类型属性，我们要求每次访问的时候都更新这个属性，显然，django的通用视图是根本不知道Author有这样的一个属性的，所以我们必须重写某个方法以增加这个行为，在这里是get\_object()方法

import datetime
    from books.models import Author
    from django.views.generic import DetailView
    from django.shortcuts import get_object_or_404
    class AuthorDetailView(DetailView):
        queryset = Author.objects.all()
        def get_object(self):
            # Call the superclass
            object = super(AuthorDetailView, self).get_object()
            # Record the last accessed date
            object.last_accessed = datetime.datetime.now()
            object.save()
            # Return the object
            return object

## 装饰基于类的视图 ##

### 在url中装饰 ###

from django.contrib.auth.decorators import login_required, permission_required
    from django.views.generic import TemplateView
    from .views import VoteView
    urlpatterns = patterns('',
        (r'^about/', login_required(TemplateView.as_view(template_name="secret.html"))),
        (r'^vote/', permission_required('polls.can_vote')(VoteView.as_view())),
    )

### 在类中装饰 ###

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, *args, **kwargs):
            return super(ProtectedView, self).dispatch(*args, **kwargs)

转载于:https://www.cnblogs.com/qwj-sysu/p/4199829.html