Django搭建简单网页的学习笔记之四（Form）


Django搭建简单网页的学习笔记之四
（使用简单表单处理数据以及使用generic views精简代码）
一、使用表单处理数据
1、为了实现投票功能，当点击某一选项时，能提交数据到vote里去处理并返回结果，需要使用表单提交数据，在之前的detail.html里写上如下代码：
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>
2、为了能找到vote的路径，需要在urls.py中设置路径：
polls/urls.py
url(r'^(?P<question_id>[0-9]+)/vote/$', views.vote, name='vote'),
3、然后在views.py的vote函数中编写代码处理数据，实现一个问题的某一选项的票数增加并存储：
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 .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):
return render(request, 'polls/detail.html', {
'question': p,
'error_message': "You didn't select a choice.",
})
else:
selected_choice.votes += 1
selected_choice.save()
return HttpResponseRedirect(reverse('polls:results', args=(p.id,)))
4、点击投票按钮后需要跳转到投票结果页面results.html，显示某个问题的得票情况，也就是显示票数，并提示是否需要继续投票，以下代码修改view.py中的results函数，处理点击投票按钮后的数据，指定返回results.html的页面：
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})

在polls的template中创建results.html，在results.html中编写如下代码：
polls/templates/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>

二、精简代码，使用generic views
接下来，我们使用如下步骤，来转变我们之前的代码：
1、改变URL配置
2、删除一些不需要的，旧的view
3、引进新的，基于Django的 generic views

第一步，修改URL配置：
首先，打开polls/urls.py，作如下修改：
polls/urls.py

from django.conf.urls import url
from . import views
urlpatterns = [
url(r'^$', views.IndexView.as_view(), name='index'),
url(r'^(?P<pk>[0-9]+)/$', views.DetailView.as_view(), name='detail'),
url(r'^(?P<pk>[0-9]+)/results/$', views.ResultsView.as_view(), name='results'),
url(r'^(?P<question_id>[0-9]+)/vote/$', views.vote, name='vote'),
]

第二步，修改view，引进新的generic views：
删除之前的函数，新建类引进generic view，实现之前函数实现的功能：
polls/views.py

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 .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'

def vote(request, question_id):
... # same as above