Finished 3.4 Using template system

first_django_app.md

@@ -207,3 +207,20 @@ Here `path()` function is passed **route** and **view**; two additional option a
 
 > 什么我们使用辅助函数 get_object_or_404() 而不是自己捕获 ObjectDoesNotExist 异常呢？还有，为什么模型 API 不直接抛出 ObjectDoesNotExist 而是抛出 Http404 呢？
 > 因为这样做会增加模型层和视图层的耦合性。指导 Django 设计的最重要的思想之一就是要保证松散耦合。一些受控的耦合将会被包含在 django.shortcuts 模块中。
+
+### 3.4 Using template system
+
+[Templates in Django](https://docs.djangoproject.com/en/3.1/topics/templates/)
+
+`polls/detail.html` 模板里正式的代码:
+
+```html
+<h1>{{ question.question_text }}</h1>
+<ul>
+{% for choice in question.choice_set.all %}
+    <li>{{ choice.choice_text }}</li>
+{% endfor %}
+</ul>
+```
+
+模板系统统一使用点符号来访问变量的属性

src/polls/templates/polls/detail.html

@@ -1 +1,6 @@
-{{ question }}
+<h1>{{ question.question_text }}</h1>
+<ul>
+{% for choice in question.choice_set.all %}
+    <li>{{ choice.choice_text }}</li>
+{% endfor %}
+</ul>

src/polls/views.py

@@ -1,20 +1,16 @@
 from django.http import request, HttpResponse
-from django.shortcuts import render
+from django.shortcuts import render, get_object_or_404
 from django.template import loader
 
 from .models import Question
 
 def index(request):
     latest_question_list = Question.objects.order_by('-pub_date')[:5]
-    template = loader.get_template('polls/index.html')
     context = {'latest_question_list': latest_question_list}
     return render(request, 'polls/index.html', context)
 
 def detail(request, question_id):
-    try:
+    question = get_object_or_404(Question, pk=question_id)
-        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):