django入门-part3

完全翻译自官方文档 https://docs.djangoproject.com/en/1.10/intro/tutorial03/

本节讲视图

我们设计一个简单投票页面,它有如下3个功能

1. 显示要投票的问题

2. 点击"投票"按钮提交你的选项

3. 展示这个投票的结果

polls/views.py 代码如下:

def detail(request, question_id):
    return HttpResponse("You‘re looking at question %s." % question_id)  #显示要投票的题目

def results(request, question_id):
    response = "You‘re looking at the results of question %s."  # 显示投票结果
    return HttpResponse(response % question_id)

def vote(request, question_id):
    return HttpResponse("You‘re voting on question %s." % question_id)  # 提交投票选项内容

polls/urls.py 代码如下

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‘),
]

一个视图只会返回 HttpResponse 或 Http404

下面写一个从数据库获取内容的view

from django.http import HttpResponse

from .models import Question

def index(request):
    latest_question_list = Question.objects.order_by(‘-pub_date‘)[:5]
    output = ‘, ‘.join([q.question_text for q in latest_question_list])
    return HttpResponse(output)

我们在代码里硬编码了页面只返回5条内容,这很外行,所以我们用django的模板系统

django默认会在这个目录结构下读取我们的模板文件

polls/templates/polls/index.html

就是在你的应用目录下创建文件夹 templates ,再在templates里创建一个跟应用名字一样的目录poolls

这个index.html的访问路径就是 polls/index.html

你的index.html内容如下:

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

相应的修改你的views.py

from django.http import HttpResponse
from django.template import loader

from .models import Question

def index(request):
    latest_question_list = Question.objects.order_by(‘-pub_date‘)[:5]
    template = loader.get_template(‘polls/index.html‘)
    context = {
        ‘latest_question_list‘: latest_question_list,
    }
    return HttpResponse(template.render(context, request))

context 就是一个字典, 模板里会使用这个变量

上面的方法稍显麻烦,先加载loader模板文件,再渲染render文件,django为我们提供了一个更方面的命令 render()

继续修改我们的使用,我们使用render重写上面的index()

from django.shortcuts import render

from .models import Question

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)

当访问的页面不存在时,我们抛一个404出去

from django.http import Http404
from django.shortcuts import render

from .models import Question
# ...
def detail(request, question_id):
    try:
        question = Question.objects.get(pk=question_id)
    except Question.DoesNotExist:
        raise Http404("Question does not exist")
    return render(request, ‘polls/detail.html‘, {‘question‘: question})

再精简代码,正常获取和抛404可以用一个方法 get_object_or_404()

from django.shortcuts import get_object_or_404, render

from .models import Question

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

类似的还有get_list_or_404(),还有最好用filter()函数代替get(),因为get()会抛一个Http404异常

模板系统开讲

polls/templates/polls/detail.html

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

用点来访问变量的属性

来看这段代码,我们在href中硬编码了访问路径

<li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>

怎么解决呢,在url()方法里加name参数

...
# the ‘name‘ value as called by the {% url %} template tag
url(r‘^(?P<question_id>[0-9]+)/$‘, views.detail, name=‘detail‘),
...

修改以后,上面的硬编码变成这样

<li><a href="{% url ‘detail‘ question.id %}">{{ question.question_text }}</a></li>

这样即使你修改了你的url路径,那么你的html也不需要修改.

URL命名空间

在一个django项目里可能包含很多应用, 那么就会出现多个url(name="这里的名字有重复"),那么怎么解决呢

from django.conf.urls import url

from . import views

app_name = ‘polls‘  # <==就是它
urlpatterns = [
    url(r‘^$‘, views.index, name=‘index‘),
    url(r‘^(?P<question_id>[0-9]+)/$‘, views.detail, name=‘detail‘),
    url(r‘^(?P<question_id>[0-9]+)/results/$‘, views.results, name=‘results‘),
    url(r‘^(?P<question_id>[0-9]+)/vote/$‘, views.vote, name=‘vote‘),
]

同时修改你的html

<li><a href="{% url ‘polls:detail‘ question.id %}">{{ question.question_text }}</a></li>

看到区别了吗

好了 本节完