django2.0入门教程第四节

继上篇 django2.0入门教程第三节，介绍了django2.0的视图views和模板template, 本节介绍如何在前台进行投票。

构建一个简单的表单提交页

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 id="choice{{ forloop.counter }}" type="radio" name="choice" value="{{ choice.id }}">
    <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br />
    {% endfor %}
    <br />
    <input type="submit" name="" id="" value="投票" />
</form>

代码解析：

• form表单提交的url为{%url 'polls:vote' question.id %}, 即表示访问polls/views.py的vote方法，并携带问题id作为参数。

• 将问题的相关选项遍历，以单选框显示

• form表单用post方式提交数据

配置url

polls/urls.py

path('<int:question_id>/vote/', views.vote, name='vote'),

投票页面截图 http://127.0.0.1:8000/polls/1/ ：

视图层处理提交结果

polls/views.py

from django.shortcuts import render, get_object_or_404
from django.http import HttpResponse, HttpResponseRedirect
from django.urls import reverse
from .models import Question, Choice
# ...
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):
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "必须选择一个选项",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))

代码解析：

• request.POST['choice']接收表单页面提交的数据

• 将投票次数加1，并更新数据库

显示投票结果

polls/views.py

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

results.html

<h1>{{ question.question_text }}</h1>
<ul>
{% for choice in question.choice_set.all %}
<li>{{ choice.choice_text }} -- {{choice.votes}}</li>
{% endfor %}
</ul>

<a href="{% url 'polls:detail' question.id %}">再投一次？</a>

提交结果页面 http://127.0.0.1:8000/polls/1/results/

优化url和view写法

另一种写法：
将主键id代替question_id

polls/urls.py

#_*_coding:utf8_*_
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'),
]

使用<pk>代替<question_id>会更加灵活，<pd>代表主键

相应的视图也需要修改成另一种写法，vote方法保持原样，用于比较两种写法的不同

polls/views.py

#_*_coding:utf8_*_
from django.shortcuts import render, get_object_or_404
from django.http import HttpResponseRedirect
from django.urls import reverse
from django.views import generic 
from .models import Question, Choice

class IndexView(generic.ListView):
    template_name = 'polls/index.html'
    context_object_name = 'latest_question_list'

    def get_queryset(self):
        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):
    # ...

入门教程不会对代码进入深入的讲解，先大致了解其作用即可，后续再逐个模块进行解析

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