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# Writing your first Django app--part 3 about view

2014-09-08 10:41 387 查看
添加更多的view

写actually有用的view

使用模版来设计view

使用模版设计view的捷径:render()

抛出异常404

抛出异常404-快捷方法: get_object_or_404()

修改URL硬编码

URL命名空间


view : Django应用(作为一个特殊的功能或者有一个特定的模版)里的一种网页.


在DemoAppPoll里,我们下面的view:

Question index page -->展示最新的问题

Question detail page -->展示一个问题和一个投票表格

Question result page --> 展示特定问题的投票结果

Vote action --> 处理特定问题的投票.

在Django里,每一个view都代表一个python 函数/方法.

请求一个url的时候,Django就会使用一个view来处理这个page.

从URL传递到view,Django使用URLconfs

第一个view

1.修改DemoAppPoll/views.py:

from django.shortcuts import render
from django.http import HttpResponse

def index(request):
return HttpResponse("Hello,urmyfatih.")

2.创建DemoAppPoll/urls.py

from django.conf.urls import patterns,url
from DemoAppPoll imoprt views

urlpatterns =patterns(
'',
url(r'^$',views.index,name='index')
)

3.在工程demoSite/urls.py中添加应用DemoAppPoll的urls.py

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

urlpatterns = patterns('',
# Examples:
# url(r'^$', 'demoSite.views.home', name='home'),
# url(r'^blog/', include('blog.urls')),
url(r'^DemoAppPoll/', include('DemoAppPoll.urls')),
url(r'^admin/', include(admin.site.urls)),

)


url(r'^DemoAppPoll/', include('DemoAppPoll.urls')),就是我们新增的.



表示,我们使用DemoAppPoll.urls来处理http://localhost:8080/DemoAppPoll/的请求.



在DemoAppPoll.urls里,我们绑定了views.index来处理请求.





url()参数:regex

python将url请求在工程里urls.py中的pattterns列表中一一匹配.

并且这种匹配不会匹配请求的参数.即http://www.example.com/myapp/?name=zx仅会匹配myapp/

url()参数:view

匹配到正则表达式之后,调用特定的view函数.

url()参数:kwargs

任意的关键字参数,可以通过字典传递给特定的view.

url()参数:name

给url命名,这样就可以全局使用.

添加更多的view

DemoAppPoll/urls.py

from django.conf.urls import patterns,url

from DemoAppPoll import views

urlpatterns = patterns('',
url(r'^$', views.index, name='index'),
url(r'^(?P<question_id>\d+)/$', views.detail, name='detail'),
url(r'^(?P<question_id>\d+)/results/$', views.results, name='results'),
url(r'^(?P<question_id>\d+)/vote/$', views.vote, name='vote'),
)

指定类/方法/函数来处理匹配到url:


views.index -->处理/DemoAppPoll/



views.detail-->处理/DemoAppPoll/[number]/



view.results-->处理/DemoAppPoll/[number]/results/



views.vote -->处理/DemoAppPoll/[number]/vote/


下面的是类/方法/函数具体如何响应请求的:

DemoAppPoll/views.py:

from django.shortcuts import render
from django.http import HttpResponse

def index(request):
return HttpResponse("Hello,urmyfatih.")

def detail(request, question_id):
return HttpResponse("You're looking at question %s." % question_id)

def results(request, question_id):
response = "You're looking at the results of question %s."
return HttpResponse(response % question_id)

def vote(request, question_id):
return HttpResponse("You're voting on question %s." % question_id)




当请求http://localhost:8080/DemoAppPoll/33/的时候,

第一步:Django加载项目下的urls.py模块,即(demoSite.urls),从demoSite/urls.py中找到代表匹配列表的变量:urlpatterns,从列表中匹配.

url(r'^DemoAppPoll/', include('DemoAppPoll.urls')),

此时,匹配到DemoAppPoll/,

当Django遇到include()的时候,截掉已经匹配到的(DemoAppPoll/),将剩余的(33/)传递到URLconf继续处理.

第二步:Django截掉前面的之后,剩下的(33/),使用DemoAppPoll.urls模块(DemoAppPoll/urls.py)来处理.

url(r'^(?P<question_id>\d+)/$', views.detail, name='detail'),

此时,匹配到view.detail,

第三步:由view.detail(DemoAppPoll/views.py中detail函数)响应请求.



写actually有用的view


每一个view做2件事情:



返回HttpResponse(它包含了真实的html内容.)

抛出一个异常,例如Http404

其他的事情就是自己安排了,例如,利用Django的数据库API,显示最新的5条问题:

#in DemoAppPoll/views.py/[fun]index

from DemoAppPoll.models import Question

def index(request):
# IMPORTANT: read db , order , limit
latest_question_list = Question.objects.order_by('-pub_date')[:5]
# format question for output.
output=','.join([p.question_text for p in latest_question_list])

return HttpResponse(output)




有个问题是,这个页面看起来是如此的简陋,这时候,可以使用template来设计.

另外一个问题是,template的位置放在哪里?


Django的TEMPLATE_LOADER设置包含了从哪里获得模版.

它的默认值有两个.


TEMPLATE_LOADERS
Default:
('django.template.loaders.filesystem.Loader',
'django.template.loaders.app_directories.Loader')


其中一个是app的,它在INSTALLED_APP的目录下查找templates目录.


使用模版来设计view

1th. 在App(DemoAppPoll)目录下,创建templates目录.

2th. 在templates目录下创建App名称(DemoAppPoll)的目录.

3th. 在DemoAppPoll目录下,创建index.html.

D:\desktop\todoList\Django\mDjango\demoSite\DemoAppPoll>tree /f /a
|   admin.py
|   admin.pyc
|   models.py
|   models.pyc
|   tests.py
|   urls.py
|   urls.pyc
|   views.py
|   views.pyc
|   __init__.py
|   __init__.pyc
|
+---migrations
|       0001_initial.py
|       0001_initial.pyc
|       __init__.py
|       __init__.pyc
|
\---templates
\---DemoAppPoll
index.html

这样,我们就可以是使用DemoAppPoll/index.html来设计view了.

4th. 修改index.html

使用for循环创建无序列表.


{% if latest_question_list %} 这是代表使用python语句.



{{ question.id }}代表使用python变量.


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

5th. 使用模版文件来渲染之后输出.

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

from DemoAppPoll.models import Question

def index(request):
# IMPORTANT: read db , order , limit
latest_question_list = Question.objects.order_by('-pub_date')[:5]
template = loader.get_template('DemoAppPoll/index.html')
context = RequestContext(
request,
{
'latest_question_list':latest_question_list,
},
)

return HttpResponse(template.render(context))

这里,涉及到如何使用哪个模版,向模版传入变量,最后渲染后输出.


python     template = loader.get_template('DemoAppPoll/index.html')     context = RequestContext(         request,         {             'latest_question_list':latest_question_list,         },         )      return HttpResponse(template.render(context))






使用模版设计view的捷径:render()


常见的习惯是:加载模版,填充内容 ,返回HttpResponse.


Django 提供了一个简洁的方法来实现,例如上面的index()方法,

from django.shortcuts import render
#from django.http import HttpResponse
#from django.template import RequestContext, loader

from DemoAppPoll.models import Question

'''
def index(request):
# IMPORTANT: read db , order , limit
latest_question_list = Question.objects.order_by('-pub_date')[:5]
template = loader.get_template('DemoAppPoll/index.html')
context = RequestContext(
request,
{
'latest_question_list':latest_question_list,
},
)

return HttpResponse(template.render(context))
'''
# render(请求,模版,参数列表字典{key:value})

def index(request):
latest_question_list = Question.objects.order_by('-pub_date')[:5] @
context = {'latest_question_list': latest_question_list}
return render(request, 'DemoAppPoll/index.html', context)


注意到,"from django.shortcuts import render"之后,就不需要"from django.http import HttpResponse"和"from django.template import RequestContext, loader"



抛出异常404

在数据库里,如果只有2条记录,那么访问第3条记录,就应该抛出异常.

在DemoAppPoll/views.py

def detail(request, question_id):
try:
question = Question.objects.get(pk=question_id)
except Question.DoesNotExist:
raise Http404
return  render(request, 'DemoAppPoll/detail.html', {'question': question})
#return HttpResponse("You're looking at question %s." % question_id)

注意

a.需要导入新包:


from django.http import Http404


b.需要创建模版文件:detail.html

<div align="center">
<table  cellpadding="0" cellspacing="0"  width="500">
<tr align="center" >
<td>question_id</td>
<td>question_text</td>
</tr>
<tr  align="center">
<td >{{question_id}}</td>
<td >{{question}}</td>
</tr>
</table>
</div>




抛出异常404-快捷方法

在DemoAppPoll/views.py

'''
def detail(request, question_id):
try:
question = Question.objects.get(pk=question_id)
except Question.DoesNotExist:
raise Http404
return  render(request, 'DemoAppPoll/detail.html', {'question': question,'question_id':question_id})
#return HttpResponse("You're looking at question %s." % question_id)
'''
def detail(request, question_id):
question = get_object_or_404(Question, pk=question_id)
return render(request, 'DemoAppPoll/detail.html', {'question': question})

这里,导入包的问题也存在,改为:

from django.shortcuts import render,get_object_or_404

多了个get_object_or_404.


question = get_object_or_404(Question, pk=question_id),得到对象



也有一个get_list_or_404() 函数,得到列表.



修改URL硬编码

在DemoAppPoll/templates/index.html中,url为硬编码.


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


在DemoAppPoll/urls.py里,我们给这个url匹配指定过了名称(name='detail')

url(r'^(?P<question_id>\d+)/$', views.detail, name='detail'),

可以使用{%url %}来生成url.

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


URL命名空间.

当多个app存在的时候,{%url%}指的是哪个?

可以在工程目录(demosite)下的urls.py中指定命名空间:

demoSite/urls.py


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

urlpatterns = patterns('',
#url(r'^DemoAppPoll/', include('DemoAppPoll.urls')),
url(r'^DemoAppPoll/', include('DemoAppPoll.urls',namespace="DemoAppPoll")),
url(r'^admin/', include(admin.site.urls)),
)

这样,模版文件中,使用url名称的时候,需要指定命名空间:

DemoAppPoll/templates/DemoAppPoll/index.html

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