3.3 Throw 404 error

first_django_app.md

@@ -180,12 +180,12 @@ Here `path()` function is passed **route** and **view**; two additional option a
 * Django use 'URLconfs' to map btw URL and Views. Details of[pURL manager](https://docs.djangoproject.com/zh-hans/3.1/topics/http/urls/)
 * URL's general form: `/newsarchive/<year>/<month>/`
 
-### Create more Views
+### 3.1 Create more Views
 
 > 当某人请求你网站的某一页面时——比如说， "/polls/34/" ，Django 将会载入 mysite.urls 模块，因为这在配置项 ROOT_URLCONF 中设置了。然后 Django 寻找名为 urlpatterns 变量并且按序匹配正则表达式。在找到匹配项 'polls/'，它切掉了匹配的文本（"polls/"），将剩余文本——"34/"，发送至 'polls.urls' URLconf 做进一步处理。在这里剩余文本匹配了 "<int:question_id>/"，使得我们 Django 以如下形式调用 polls.urls.detail():
 > `detail(request=<HttpRequest object>, question_id=34)`
 
-### Create a true useful View
+### 3.2 Create a true useful View
 
 每个视图必须要做的只有两件事：返回一个包含被请求页面内容的 HttpResponse 对象，或者抛出一个异常，比如 Http404 。至于你还想干些什么，随便你。
 
@@ -193,8 +193,13 @@ Here `path()` function is passed **route** and **view**; two additional option a
 
 `django.shortcuts.render` 可以“载入模板，填充上下文，再返回由它生成的 HttpResponse 对象“
 
-### shortcut function: `render()`
+#### shortcut function: `render()`
 
 「载入模板，填充上下文，再返回由它生成的 HttpResponse 对象」是一个非常常用的操作流程。于是 Django 提供了一个快捷函数 render
 
-> The render() function takes the request object as its first argument, a template name as its second argument and a dictionary as its optional third argument. It returns an HttpResponse object of the given template rendered with the given context.
+> The render() function takes the request object as its first argument, a template name as its second argument and a dictionary as its optional third argument. It returns an HttpResponse object of the given template rendered with the given context.
+
+### 3.3 Throw 404 error
+
+如果指定问题 ID 所对应的问题不存在，这个视图就会抛出一个 Http404 异常。
+

src/polls/templates/polls/detail.html

@@ -0,0 +1 @@
+{{ question }}

src/polls/views.py

@@ -11,7 +11,11 @@ def index(request):
     return render(request, 'polls/index.html', context)
 
 def detail(request, question_id):
-    return HttpResponse("You're looking at question %s." % question_id)
+    try:
+        question = Question.objects.get(pk=question_id)
+    except Question.DoesNotExist:
+        raise Http404("Question does not exist")
+    return render(request, 'polls/detail.html', {'question': question})
 
 def results(request, question_id):
     response = "You're looking at the results of question %s."