Django(part4)

1. 一个简单的form表单:
   #polls/templates/polls/detail.html
   <h1>{{ question.question_text }}</h1>

   {% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %}
    <form action="{% url 'polls:vote' question.id %}" method="post"> 

   {% csrf_token %} 
   {% for choice in question.choice_set.all %} 
   <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}" /> 
   <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br /> 

   {% endfor %} 
   <input type="submit" value="Vote" /> 
   </form>

   • forloop.counter:表示for循环执行的次数
   • action="{% url 'polls:vote' question.id %}":指定处理post 数据的url
   • {% csrf_token %}:用于防止csrf攻击的tag,所有post的form都应该使用
2. 处理post的代码:

   #polls/urls.py
   url(r'^(?P<question_id>\d+)/vote/$', views.vote, name='vote'),
   
   #polls/views.py
   from django.shortcuts import get_object_or_404, render
   from django.http import HttpResponseRedirect, HttpResponse
   from django.core.urlresolvers import reverse
   
   from polls.models import Choice, Question
   # ...
   def vote(request, question_id):
       p = get_object_or_404(Question, pk=question_id)
       try:
           selected_choice = p.choice_set.get(pk=request.POST['choice'])
       except (KeyError, Choice.DoesNotExist):
           # Redisplay the question voting form.
           return render(request, 'polls/detail.html', {
               'question': p,
               'error_message': "You didn't select a choice.",
           })
       else:
           selected_choice.votes += 1
           selected_choice.save()
           # Always return an HttpResponseRedirect after successfully dealing
           # with POST data. This prevents data from being posted twice if a
           # user hits the Back button.
           return HttpResponseRedirect(reverse('polls:results', args=(p.id,)))

   # polls/view.py

   from  django.shortcuts import get_object_or_404, render
   
   def results(request, question_id):
       question = get_object_or_404(Question, pk=question_id)
       return render(request, 'polls/results.html', {'question': question})

   • request.POST:用于获取表单的值，同样的属性还有request.GET
   • request.POST[‘choice’]:choice是key值，不存在时引发KeyError exception
   • HttpResponseRedirect():参数是一个重定向的url\
   • reverse():返回一个url，通过使用url name避免hardcode
3. Generic view:

   from django.shortcuts import get_object_or_404, render
   from django.http import HttpResponseRedirect
   from django.core.urlresolvers import reverse
   from django.views import generic
   
   from polls.models import Choice, Question
   
   class IndexView(generic.ListView):
       template_name = 'polls/index.html'
       context_object_name = 'latest_question_list'
   
       def get_queryset(self):
           """Return the last five published questions."""
           return Question.objects.order_by('-pub_date')[:5]
   
   class DetailView(generic.DetailView):
       model = Question
   #template_name 告诉django自动生成的template的name
   #如果不指定默认为<app name>/<model name>_detail.html
       template_name = 'polls/detail.html'
   
   #polls/urls.py
   #注意必须用<pk>指定匹配的组名
   urlpatterns = patterns('',
       url(r'^$', views.IndexView.as_view(), name='index'),
       url(r'^(?P<pk>\d+)/$', views.DetailView.as_view(), name='detail'),
   
   )

4. 静态文件:django的STATICFILES_FINDERS setting保存了一系列finder,这些finder知道如何去查找静态文件。如AppDirectoriesFinder就会在INSTALLED_APPS包含的app的子目录下查找static目录。通常用如下存放静态文件，polls/static/polls/style.css或者polls/static/polls/images/background.gif，这样AppDirectoriesFinder可以找到,路径中第二个polls相当于静态文件的名字空间

   #polls/templates/polls/index.html
   {% load staticfiles %}
   <link rel="stylesheet" type="text/css" href="{% static 'polls/style.css' %}" />

5. How to packaging your app:参考https://docs.djangoproject.com/en/1.7/intro/reusable-apps/