writing_first_django_app_part4
Write a simple form
点击每个Question进去detail界面，看到的vote我们希望以选择的形式给用户进行选择，然后将结果以表格的形式POST到服务器．
# 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>
上面的代码有点复杂，需要注意几个地方． url ‘polls:vote‘ question.id 是表格提交的地址 {% csrf_token %} : django中防止csrd攻击的语句 每个按钮的value是choice.id，名字是chioce，所以post的时候以关键字choice=#的形式 forloop.counter表示for标签进入循环的次数
现在真正来实现vote类来处理提交的表单：
# 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,)))
最后的在选择vote提交之后将会进行重定向，url是polls:results，这个语法就是前面用过的作用域加上url名字。前面在urls.py中有url(r‘^(?P<question_id>\d+)/results/$‘, views.results, name = ‘results‘)，所以加上args=(p.id,)之后会得到类似这样的url: ‘polls/2/results/‘
要重定向到result界面，所以要在view中实现results类来处理：
# polls/views.py
from django.shortcuts import get_object_or_404, render
def results(request, question_id):
question = get_object_or_404(Question, pk=question_id)
return render(request, ‘polls/results.html‘, {‘question‘: question})
/polls/results.html:
<h1>{{ question.question_text }}</h1>
<ul>
{% for choice in question.choice_set.all %}
<li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{% endfor %}
</ul>
<a href="{% url ‘polls:detail‘ question.id %}">Vote again?</a>
这里很简单就是显示question中每个vote和它的结果，点击vote again会再次进入detail界面来选择vote
Use generic views
使用通用的views可以省去我们自己写view的步骤，我们可以让我们的poll应用使用通用views系统，需要三个步骤：
- 转化URLconf
- 删除旧的无用的views
- 使用新的views基于generic views
Amend URLconf
首先修改polls/urls.py:
from django.conf.urls import patterns, url
from polls import views
urlpatterns = patterns(‘‘,
url(r‘^$‘, views.IndexView.as_view(), name=‘index‘),
url(r‘^(?P<pk>\d+)/$‘, views.DetailView.as_view(), name=‘detail‘),
url(r‘^(?P<pk>\d+)/results/$‘, views.ResultsView.as_view(), name=‘results‘),
url(r‘^(?P<question_id>\d+)/vote/$‘, views.vote, name=‘vote‘),
)
将原来的question_id变成了pk,因为DetailView view认为从URL中抓取的关键字因该是"pk".
然后修改polls/view.py，将原来的index,detail,results类删掉，添加：
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 = ‘polls/detail.html‘
class ResultsView(generic.DetailView):
model = Question
template_name = ‘polls/results.html‘
我们使用了两个generic views: ListView, DetailView IndexView类还是使用index.html模板进行渲染，index.html中有参数latest_question_list,所以要对context_object_name进行赋值，说明文本对象的名字。 查看IndexView里面get_queryset的用法如下：
Get the list of items for this view. This must be an iterable and may be a queryset (in which queryset-specific behavior will be enabled).
即获取当前view需要的item列表