Django模块笔记【二】

入门笔记翻译整理自：https://docs.djangoproject.com/en/1.8/topics/

*该笔记将对各个模块进行单独介绍

* HTTP Request Handlers

1. URL dispatcher

URL在名为URLconf的Python模块中创建，该模块提供了URL模式（正则表达式）和Python函数（视图）之间的映射。

URLconf举例如下：

 1 from django.conf.urls import url
 2 
 3 from . import views
 4 
 5 urlpatterns = [
 6     url(r'^articles/2003/$', views.special_case_2003),
 7     url(r'^articles/([0-9]{4})/$', views.year_archive),
 8     url(r'^articles/([0-9]{4})/([0-9]{2})/$', views.month_archive),
 9     url(r'^articles/([0-9]{4})/([0-9]{2})/([0-9]+)/$', views.article_detail),
10 ]

可以为对模式进行命名，以方便之后作为命名参数使用：

 1 from django.conf.urls import url
 2 
 3 from . import views
 4 
 5 urlpatterns = [
 6     url(r'^articles/2003/$', views.special_case_2003),
 7     url(r'^articles/(?P<year>[0-9]{4})/$', views.year_archive),
 8     url(r'^articles/(?P<year>[0-9]{4})/(?P<month>[0-9]{2})/$', views.month_archive),
 9     url(r'^articles/(?P<year>[0-9]{4})/(?P<month>[0-9]{2})/(?P<day>[0-9]{2})/$', views.article_detail),
10 ]

可以使用include来包含其他URLconfs:

1 from django.conf.urls import include, url
2 
3 urlpatterns = [
4     # ... snip ...
5     url(r'^community/', include('django_website.aggregator.urls')),
6     url(r'^contact/', include('django_website.contact.urls')),
7     # ... snip ...
8 ]

可以使用include进行代码简化：

 1 from django.conf.urls import include, url
 2 from . import views
 3 
 4 urlpatterns = [
 5     url(r'^(?P<page_slug>[w-]+)-(?P<page_id>w+)/', include([
 6         url(r'^history/$', views.history),
 7         url(r'^edit/$', views.edit),
 8         url(r'^discuss/$', views.discuss),
 9         url(r'^permissions/$', views.permissions),
10     ])),
11 ]

URLconf的参数具有继承关系：

 1 # In settings/urls/main.py
 2 from django.conf.urls import include, url
 3 
 4 urlpatterns = [
 5     url(r'^(?P<username>w+)/blog/', include('foo.urls.blog')),
 6 ]
 7 
 8 # In foo/urls/blog.py
 9 from django.conf.urls import url
10 from . import views
11 
12 urlpatterns = [
13     url(r'^$', views.blog.index),
14     url(r'^archive/$', views.blog.archive),
15 ]

可以在URLconf中设置嵌套参数，注意以下两者的不同：

1 from django.conf.urls import url
2 
3 urlpatterns = [
4     url(r'blog/(page-(d+)/)?$', blog_articles),                  # bad
5     url(r'comments/(?:page-(?P<page_number>d+)/)?$', comments),  # good
6 ]

可以对URL传入参数：

1 from django.conf.urls import url
2 from . import views
3 
4 urlpatterns = [
5     url(r'^blog/(?P<year>[0-9]{4})/$', views.year_archive, {'foo': 'bar'}),
6 ]

也可以对URL进行空间命名（namespaced URLs），这里略过。

———————————————————————————————————————————————————————————————————————————————————————————

2. 写入视图（Writing views）

通过例子说明用法：

1 from django.http import HttpResponse
2 import datetime
3 
4 def current_datetime(request):
5     now = datetime.datetime.now()
6     html = "<html><body>It is now %s.</body></html>" % now
7     return HttpResponse(html)

1 from django.http import HttpResponse, HttpResponseNotFound
2 
3 def my_view(request):
4     # ...
5     if foo:
6         return HttpResponseNotFound('<h1>Page not found</h1>')
7     else:
8         return HttpResponse('<h1>Page was found</h1>')

可以很容易自定义错误视图，这里略过。

3. 视图装饰器（View decorators）

装饰器可以限制访问视图的方式：

1 from django.views.decorators.http import require_http_methods
2 
3 @require_http_methods(["GET", "POST"])
4 def my_view(request):
5     # I can assume now that only GET or POST requests make it this far
6     # ...
7     pass

除了@require_http_methods装饰器之外，还有其他较为复杂的装饰器，这里略过。

4. 文件上传

基本的上传方法：

 1 from django.http import HttpResponseRedirect
 2 from django.shortcuts import render_to_response
 3 from .forms import UploadFileForm
 4 
 5 # Imaginary function to handle an uploaded file.
 6 from somewhere import handle_uploaded_file
 7 
 8 def upload_file(request):
 9     if request.method == 'POST':
10         form = UploadFileForm(request.POST, request.FILES)
11         if form.is_valid():
12             handle_uploaded_file(request.FILES['file'])
13             return HttpResponseRedirect('/success/url/')
14     else:
15         form = UploadFileForm()
16     return render_to_response('upload.html', {'form': form})

处理模型中的上传文件（uploaded files）:

 1 from django.http import HttpResponseRedirect
 2 from django.shortcuts import render
 3 from .forms import ModelFormWithFileField
 4 
 5 def upload_file(request):
 6     if request.method == 'POST':
 7         form = ModelFormWithFileField(request.POST, request.FILES)
 8         if form.is_valid():
 9             # file is saved
10             form.save()
11             return HttpResponseRedirect('/success/url/')
12     else:
13         form = ModelFormWithFileField()
14     return render(request, 'upload.html', {'form': form})

5. Django简便函数（shortcut functions）

render()函数将给定模板和给定环境字典结合，返回被渲染文本的HttpResponse对象。

render_to_response()函数和render()函数功能类似。

redirect()函数向合适的URL返回HttpResponseRedirect对象。

get_object_or_404()函数在给定模型管理器上调用get()函数，但是它抛出Http404错误而不是模型DoesNotExist异常。

get_list_or_404()函数将给定模型管理器上filter()的结果返回给列表，如果结果为空，则抛出Http404错误。

6. 通用视图（generic views）

略。

7. 中间件（Middleware）

在设置中，向MIDDLWARE_CLASSES元组中添加中间件，中间件顺序很重要。

在请求阶段（request phase），Django会在调用视图之前依次应用中间件。

在响应阶段（response phase），Django会在调用视图之后逆序依次应用中间件。如下图：

middleware application order

这两个过程总共涉及5个方法：process_request, process_view; process_template_response, process_response, process_exception。

8. 怎样使用会话（sessions）

会话分为file based sessions和cache based sessions。此处略过。

-- the end --