Views#3-通过类编写的视图函数

Class-based views

官方推荐使用通用视图类

• 简单示例

  # 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 __str__(self):              # __unicode__ on Python 2
          return self.name
  

  # views.py
  from django.views.generic import ListView
  from books.models import Publisher
  
  class PublisherList(ListView):
      # model类属性指定了使用的数据模型
      model = Publisher
      # 如不指定template_name属性，Django会自动为该类指定一个模板路径（比方该类的默认路径为"books/publisher_list.html"，books是app名称）
      # 同时会自动将查找的结果指向'object_list'变量，从而可以在模板中直接使用
  

  # urls.py
  from django.conf.urls import url
  from books.views import PublisherList
  
  urlpatterns = [
      # PublisherList并不是视图函数，因此不能直接调用，而需要调用as_view()类方法
      url(r'^publishers/$', PublisherList.as_view()),
  ]
  

  ---

• 指定模板使用的环境变量名

  class PublisherList(ListView):
      model = Publisher
      # 通过context_object_name类属性来指定
      context_object_name = 'my_favorite_publishers'
  

• 添加额外的环境变量
  重载get_context_data()方法

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

• 指定视图类使用的对象
  除了使用model属性外，通过queryset属性也可以指定视图类处理的对象

  from django.views.generic import ListView
  from books.models import Book
  
  class BookList(ListView):
      # 该视图类处理的对象由queryset指定，这样做的好处是可以更明确地处理返回结果
      queryset = Book.objects.order_by('-publication_date')
      context_object_name = 'book_list'
  

• 自动筛选对象
  如果通过model或者queryset来指定查找对象，面对不同的筛选条件，需要定义不同的视图类，这样做就会显得很繁琐
  Django提供了get_queryset()方法来处理不同的筛选条件

  当调用视图类时，绝大多数的信息将保存在self中（如self.request）；其中self.args将保存URLconf传入的位置参数，self.kwargs将保存URLconf传入的关键字参数

  # urls.py
  urlpatterns = [
      # 正则表达式中有一个位置参数，将保存到其调用的视图类（PublisherBookList）的self.args中
      url(r'^books/([\w-]+)/$', PublisherBookList.as_view()),
  ]
  

  # views.py
  from django.shortcuts import get_object_or_404
  from django.views.generic import ListView
  from books.models import Book, Publisher
  
  class PublisherBookList(ListView):
  
      template_name = 'books/books_by_publisher.html'
  
      # 该方法返回视图类的处理对象
      def get_queryset(self):
          # 此处用self的publisher属性指向所得结果是为了在后续方法中也可以使用该对象
          # self.args保存的是位置参数列表
          self.publisher = get_object_or_404(Publisher, name=self.args[0])
          return Book.objects.filter(publisher=self.publisher)
  
      # 该方法添加环境变量
      def get_context_data(self, **kwargs):
          # Call the base implementation first to get a context
          context = super(PublisherBookList, self).get_context_data(**kwargs)
          # Add in the publisher
          # 此处就使用到了上文中定义的self.publisher对象
          context['publisher'] = self.publisher
          return context
  

• 对象预处理/善后
  get_object()方法可以获得将要处理的对象，通过对该方法的重载，可以对对象进行一些额外的处理

  # urls.py
    urlpatterns = [
      # 对于DetailView的视图类，需要通过pk关键字参数（django默认为pk，也可以指定为其它）来指定所需的对象
      url(r'^authors/(?P<pk>[0-9]+)/$', AuthorDetailView.as_view(), name='author-detail'),
  ]
  

  # views.py
  from django.views.generic import DetailView
  from django.utils import timezone
  from books.models import Author
  
  class AuthorDetailView(DetailView):
  
      # 指定处理对象（实质上是model=Author的另一种表现）
      queryset = Author.objects.all()
  
      # 该方法可用于对对象属性的一些处理
      def get_object(self):
          # Call the superclass
          object = super(AuthorDetailView, self).get_object()
          # Record the last accessed date
          object.last_accessed = timezone.now()
          object.save()
          # 最终需要返回对象本身
          return object
  

• 通用编辑视图
  主要用于表单视图
  • FormView
  • CreateView
  • UpdateView
  • DeleteView
    主要通过视图类来处理表单
• 基础表单

  # forms.py
  from django import forms
  
  class ContactForm(forms.Form):
      name = forms.CharField()
      message = forms.CharField(widget=forms.Textarea)
  
      def send_eamil(self):
          # send email using the self.cleaned_data dictionary
          pass
  

  对于上述表单可以通过FormView来创建视图

  # views.py
  from myapp.forms import ContactForm
  from django.views.generic.edit import FormView
  
  class ContactView(FormView):
      template_name = 'contact.html'
      # form_class指定自定义的表单
      # 也可以通过指定model、queryset属性或者重载get_object()方法来使用Django自动生成的表单
      form_class = ContactForm
      # 若表单提交成功，将会转向success_url页面
      success_url = '/thanks/'
  
      # 该方法用于自动提交合理表单（可以重载）
      def form_valid(self, form):
          # This method is called when valid form data has been POSTed.
          # It should return an HttpResponse.
          form.send_email()
          return super(ContactView, self).form_valid(form)
  

  对于实现了get_absolute_url()方法的数据模型，CreateView或者UpdateView视图函数都无需指定success_url属性

  # models.py
  from django.urls import reverse
  from django.db import models
  
  class Author(models.Model):
      name = models.CharField(max_length=200)
  
      def get_absolute_url(self):
          return reverse('author-detail', kwargs={'pk': self.pk})
  

  # views.py
  from django.views.generic.edit import CreateView, UpdateView, DeleteView
  from django.urls import reverse_lazy
  from myapp.models import Author
  
  # AuthorCreate和AuthorUpdate表单在成功提交会，会自动转向get_absolute_url()方法返回的页面
  class AuthorCreate(CreateView):
      model = Author
      # fields的用法和ModelForm的Meta类中定义的fields属性一致；
      # 若ModelForm中没有定义fields属性（即自动生成ModelForm时），则需要在Generic editing views中显示指定
      # 因此，若在同一个视图类中同时指定fields和form_class属性，会引发ImproperlyConfigured异常
      fields = ['name']
      # 可以通过指定template_name属性来设置使用的模板
      # 此处并未指定，因此AuthorCreate和AuthorUpdate类默认使用myapp/author_form.html
      # AuthorDelete类会默认使用myapp/author_confirm_delete.html
  
  class AuthorUpdate(UpdateView):
      model = Author
      fields = ['name']
  
  class AuthorDelete(DeleteView):
      model = Author
      success_url = reverse_lazy('author-list')
  

  # urls.py
  urlpatterns = [
      # URLconf的设置同DetailView一致，需要传入pk关键字参数指定使用的具体数据
      url(r'author/add/$', AuthorCreate.as_view(), name='author-add'),
      url(r'author/(?P<pk>[0-9]+)/$', AuthorUpdate.as_view(), name='author-update'),
      url(r'author/(?P<pk>[0-9]+)/delete/$', AuthorDelete.as_view(), name='author-delete'),
  ]
  

• 通用日期视图
  主要用于展示归档信息
  • ArchiveindexView
  • YearArchiveView
  • MonthArchiveView
  • WeekArchiveView
  • DayArchiveView
  • TodayArchiveView
  • DateDetailView
• Class-based views mixins
• Class-based generic views