Django tutorial part4

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