Django App(四) Submit a form

      经过前面的努力,到这里我们已经基本完成了,从服务器到浏览器的数据下发,还没有解决从浏览器到服务器的数据上传,这一节将创建一个Form获取从浏览器提交的数据

    1.新建Form

       接着前面建的项目,网上调查,每一个Question有多个Choice,当用户针对特定问题,可以提交选择,数据库记录每个Choice的vote数,所以新建:

       polls/templates/detail.html  

       编写代码如下: 

<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>

      {% csrf_token %} django为了防止跨站点伪造请求,POST Form 应当在请求中使用{% csrf_token%}标签

      {% url 'polls:vote' question.id %}的写法,是为了防止页面硬编码[查看上一篇内容],引入的url的另一种写法, polls:vote 的写法是给polls/urls.py 加了url命名空间:

from django.urls import path
from . import views
app_name="polls"
urlpatterns=[
    path('',views.index,name='index'),
    path('<int:question_id>/detail',views.detail,name="detail"), #定义detail view
    path('<int:question_id>/results',views.results,name='results'),#定义格式:/参数[参数类型为int]/results
    #这里将原来的vote/<int:question_id>改成<Vote/<int:question_id>
    path('vote/<int:question_id>',views.vote,name='vote')  #定义格式:vote/参数[参数类型为int]
]

        上面建的表单要提交一个question_id 和 Choice_Id 到 /vote view,为了表单提交数据的安全性,这里指定使用POST传输,这点view没有特别要求,改造view/vote 对指定的question_id的choice_id的votes+1

      2.接收Form数据并处理业务

         修改polls/views.py/vote如下,(为了方便对比这里贴出来整个Views.py): 

from django.shortcuts import get_object_or_404, render
from django.http import HttpResponseRedirect, HttpResponse
from django.urls import reverse

from .models import Choice, Question
# ...
def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            '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=(question.id,)))

def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]

    context = {
        'latest_question_list': latest_question_list,
    }
    return  render(request,'polls/index.html',context)
# ...
def detail(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/detail.html', {'question': question})

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

            编辑polls/templates/polls/index.html如下:

{% if latest_question_list %}
    <ul>
    {% for question in latest_question_list %}
        <li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>
    {% endfor %}
    </ul>
{% else %}
    <p>No polls are available.</p>
{% endif %}

            以上完成了投票功能,最后需要对投票的结果进行展示,新建网页: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>

            启动站点,浏览http://localhost:8000/polls/

            

               投票完成之后,查询数据:

               

             3.view改良

               首先每张表都有主键,对polls/urls.py的改良就是将<int:question_id>替换成<int:pk>

from django.urls import path

from . import views

app_name = 'polls'
urlpatterns = [
    path('', views.IndexView.as_view(), name='index'),
    path('<int:pk>/', views.DetailView.as_view(), name='detail'),
    path('<int:pk>/results/', views.ResultsView.as_view(), name='results'),
    path('<int:question_id>/vote/', views.vote, name='vote'),
]

              polls/views.py中原来定义的index,detail,results 换成 Django generic的view 

from django.shortcuts import get_object_or_404, render
from django.http import HttpResponseRedirect
from django.urls import reverse
from django.views import generic
from django.utils import timezone

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):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            '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=(question.id,)))

              view vote牵涉到表单提交,数据库的操作,所以没有使用通用view改造