django用户投票系统详解

投票系统之详解

1、创建项目（mysite）与应用（polls）

django-admin.py startproject mysite
python manage.py startapp polls

添加到setting.py

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'polls',
)

2、创建模型（即数据库）

一般web开发先设计数据库，数据库设计好了，项目就完了大半了，可见数据库的重要性。打开polls/models.py编写如下：

 coding=utf-8
from django.db import models

# Create your models here.
# 问题
class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')

    def __unicode__(self):
        return self.question_text

# 选择
class Choice(models.Model):
    question = models.ForeignKey(Question)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

    def __unicode__(self):
        return self.choice_text

执行数据库表生成与同步。

python manage.py makemigrations polls
python manage.py syncdb

3、admin管理

　django提供了强大的后台管理，对于web应用来说，后台必不可少，例如，当前投票系统，如何添加问题与问题选项？直接操作数据库添加，显然麻烦，不方便，也不安全。所以，管理后台就可以完成这样的工作。

打开polls/admin.py文件，编写如下内容：

from django.contrib import admin
from .models import Question, Choice

# Register your models here.
class ChoiceInline(admin.TabularInline):
    model = Choice
    extra = 3

class QuestionAdmin(admin.ModelAdmin):
    fieldsets = [
        (None,               {'fields': ['question_text']}),
        ('Date information', {'fields': ['pub_date'], 'classes': ['collapse']}),
    ]
    inlines = [ChoiceInline]
    list_display = ('question_text', 'pub_date')

admin.site.register(Choice)
admin.site.register(Question, QuestionAdmin)

　　当前脚本的作用就是将模型（数据库表）交由admin后台管理。

运行web容器：

登录后台：http://127.0.0.1:8000/admin

登录密码就是在执行数据库同步时设置的用户名和密码。

点击“add”添加问题。

4、编写视图

视图起着承前启后的作用，前是指前端页面，后是指后台数据库。将数据库表中的内容查询出来显示到页面上。

编写polls/views.py文件：

# coding=utf-8
from django.shortcuts import render, get_object_or_404
from django.http import HttpResponseRedirect, HttpResponse
from django.core.urlresolvers import reverse
from .models import Question, Choice

# Create your views here.
# 首页展示所有问题
def index(request):
    # latest_question_list2 = Question.objects.order_by('-pub_data')[:2]
    latest_question_list = Question.objects.all()
    context = {'latest_question_list': latest_question_list}
    return render(request, 'polls/index.html', context)

# 查看所有问题
def detail(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/detail.html', {'question': question})

# 查看投票结果
def results(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    return render(request, 'polls/results.html', {'question': question})

# 选择投票
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,)))

5、配置url

url是一个请求配置文件，页面中的请求转交给由哪个函数处理，由该文件决定。

　首先配置polls/urls.py(该文件需要创建)

from django.conf.urls import url
from . import views

urlpatterns = [
    # ex : /polls/
    url(r'^$', views.index, name='index'),
    # ex : /polls/5/
    url(r'^(?P<question_id>[0-9]+)/$', views.detail, name='detail'),
    # ex : /polls/5/results/
    url(r'^(?P<question_id>[0-9]+)/results/$', views.results, name='results'),
    # ex : /polls/5/vote
    url(r'^(?P<question_id>[0-9]+)/vote/$', views.vote, name='vote'),
]

　接着，编辑mysite/urls.py文件。

from django.conf.urls import include, url
from django.contrib import admin

urlpatterns = [
    url(r'^polls/', include('polls.urls', namespace="polls")),
    url(r'^admin/', include(admin.site.urls)),
]

6、创建模板

模板就是前端页面，用来将数据显示到web页面上。

首先创建polls/templates/polls/目录，分别在该目录下创建index.html、detail.html和results.html文件。

index.html

{% 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 %}

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>

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>

7、功能展示

启动web容器，访问：http://127.0.0.1:8000/polls/