Django官方文档学习笔记:Tutorial: Part 3
继续折腾官方文档教程上的投票应用,这回主要是讲如何创建django的视图(views)。view是django应用中网页的一种类型,每个view有一个特定的模板,服务于一个特定的方法。
投票系统这个应用比较简洁,主要有以下4个views:
- Poll “index” page – displays the latest few polls.
- Poll “detail” page – displays a poll question, with no results but with a form to vote.
- Poll “results” page – displays results for a particular poll.
- Vote action – handles voting for a particular choice in a particular poll.
1、写第一个view
修改“ polls/views.py”文件,输出hello world。
from
django.http
import
HttpResponse
def index(request):
return HttpResponse( " Hello, world. poll index. " );
修改poll应用的url文件("
polls/urls.py"):
def index(request):
return HttpResponse( " Hello, world. poll index. " );
from
django.conf.urls
import
patterns, url
from polls import views
urlpatterns = patterns( '' ,
url(r ' ^$ ' , views.index, name = ' index ' ),
)
修改项目的url文件("
mysite/urls.py"):
from polls import views
urlpatterns = patterns( '' ,
url(r ' ^$ ' , views.index, name = ' index ' ),
)
from
django.conf.urls
import
patterns, include, url
# Uncomment the next two lines to enable the admin:
from django.contrib import admin
admin.autodiscover()
urlpatterns = patterns( '' ,
# Examples:
# url(r'^$', 'mysite.views.home', name='home'),
# url(r'^mysite/', include('mysite.foo.urls')),
# Uncomment the admin/doc line below to enable admin documentation:
# url(r'^admin/doc/', include('django.contrib.admindocs.urls')),
# Uncomment the next line to enable the admin:
url(r ' ^polls/ ' , include( ' polls.urls ' )),
url(r ' ^admin/ ' , include(admin.site.urls)),
)
# Uncomment the next two lines to enable the admin:
from django.contrib import admin
admin.autodiscover()
urlpatterns = patterns( '' ,
# Examples:
# url(r'^$', 'mysite.views.home', name='home'),
# url(r'^mysite/', include('mysite.foo.urls')),
# Uncomment the admin/doc line below to enable admin documentation:
# url(r'^admin/doc/', include('django.contrib.admindocs.urls')),
# Uncomment the next line to enable the admin:
url(r ' ^polls/ ' , include( ' polls.urls ' )),
url(r ' ^admin/ ' , include(admin.site.urls)),
)
从上述代码可以看出,
视图通过HttpResponse对象来显示页面。http访问时,url则是先通过项目的url文件("
mysite/urls.py")正则表达式匹配过滤,再到具体应用的urls文件匹配视图。
url()方法参数:regex,view,kwargs,name
regex 正则表达式匹配url链接(不含参数)。例如访问“
http://www.example.com/myapp/?page=3
view 视图。url访问时,Django匹配到对应的url链接,则会调用其对应的view方法;
kwargs 传递给目标view的参数;
name 给url命名,以便于识别;
2、写多个views
请求的url根据正则表达式匹配对应的视图。
修改poll应用的views文件("
polls/views.py"):
index演示了查询最近5条poll记录,并把poll的question以逗号连接返回到页面。
from
django.http
import
HttpResponse
from polls.models import Poll
def index(request):
latest_poll_list = Poll.objects.order_by( ' -pub_date ' )[: 5 ]
output = ' , ' .join([p.question for p in latest_poll_list])
return HttpResponse(output)
def detail(request, poll_id):
return HttpResponse( " You're looking at poll %s. " % poll_id)
def results(request, poll_id):
return HttpResponse( " You're looking at the results of poll %s. " % poll_id)
def vote(request, poll_id):
return HttpResponse( " You're voting on poll %s. " % poll_id)
from polls.models import Poll
def index(request):
latest_poll_list = Poll.objects.order_by( ' -pub_date ' )[: 5 ]
output = ' , ' .join([p.question for p in latest_poll_list])
return HttpResponse(output)
def detail(request, poll_id):
return HttpResponse( " You're looking at poll %s. " % poll_id)
def results(request, poll_id):
return HttpResponse( " You're looking at the results of poll %s. " % poll_id)
def vote(request, poll_id):
return HttpResponse( " You're voting on poll %s. " % poll_id)
修改poll应用的url文件(" polls/urls.py"):
from
django.conf.urls
import
patterns, url
from polls import views
urlpatterns = patterns( '' ,
# ex: /polls/
url(r ' ^$ ' , views.index, name = ' index ' ),
# ex: /polls/5/
url(r ' ^(?P<poll_id>\d+)/$ ' , views.detail, name = ' detail ' ),
# ex: /polls/5/results/
url(r ' ^(?P<poll_id>\d+)/results/$ ' , views.results, name = ' results ' ),
# ex: /polls/5/vote/
url(r ' ^(?P<poll_id>\d+)/vote/$ ' , views.vote, name = ' vote ' ),
)
from polls import views
urlpatterns = patterns( '' ,
# ex: /polls/
url(r ' ^$ ' , views.index, name = ' index ' ),
# ex: /polls/5/
url(r ' ^(?P<poll_id>\d+)/$ ' , views.detail, name = ' detail ' ),
# ex: /polls/5/results/
url(r ' ^(?P<poll_id>\d+)/results/$ ' , views.results, name = ' results ' ),
# ex: /polls/5/vote/
url(r ' ^(?P<poll_id>\d+)/vote/$ ' , views.vote, name = ' vote ' ),
)
3、使用模板来展示页面
为了提高效率,使用模板功能来定义html页面布局。
创建index模板文件("polls/templates/polls/index.html"):
{% if latest_poll_list %}
< ul >
{% for poll in latest_poll_list %}
< li >< a href ="/polls/{{ poll.id }}/" > {{ poll.question }} </ a ></ li >
{% endfor %}
</ ul >
{% else %}
< p > No polls are available. </ p >
{% endif %}
< ul >
{% for poll in latest_poll_list %}
< li >< a href ="/polls/{{ poll.id }}/" > {{ poll.question }} </ a ></ li >
{% endfor %}
</ ul >
{% else %}
< p > No polls are available. </ p >
{% endif %}
html模板中使用了django的标记语言。views中会载入模板渲染,填充数据到标记,生成最终的web页面返回。
修改views的index方法("polls/views.py"):
from
django.http
import
HttpResponse
from django.template import Context, loader
from polls.models import Poll
def index(request):
latest_poll_list = Poll.objects.order_by( ' -pub_date ' )[: 5 ]
template = loader.get_template( ' polls/index.html ' )
context = Context({
' latest_poll_list ' : latest_poll_list,
})
return HttpResponse(template.render(context))
from django.template import Context, loader
from polls.models import Poll
def index(request):
latest_poll_list = Poll.objects.order_by( ' -pub_date ' )[: 5 ]
template = loader.get_template( ' polls/index.html ' )
context = Context({
' latest_poll_list ' : latest_poll_list,
})
return HttpResponse(template.render(context))
方法简化:render()
这是个可以简化views中生成页面的API,让代码更简洁一点。
from
django.shortcuts
import
render
from polls.models import Poll
def index(request):
latest_poll_list = Poll.objects.order_by( ' -pub_date ' )[: 5 ]
context = { ' latest_poll_list ' : latest_poll_list}
return render(request, ' polls/index.html ' , context)
from polls.models import Poll
def index(request):
latest_poll_list = Poll.objects.order_by( ' -pub_date ' )[: 5 ]
context = { ' latest_poll_list ' : latest_poll_list}
return render(request, ' polls/index.html ' , context)
4、抛出404异常
detail视图找不到匹配poll请求时,返回一个http404异常。
from
django.http
import
Http404
def detail(request, poll_id):
try :
poll = Poll.objects.get(pk = poll_id)
except Poll.DoesNotExist:
raise Http404
return render(request, ' polls/detail.html ' , { ' poll ' : poll})
def detail(request, poll_id):
try :
poll = Poll.objects.get(pk = poll_id)
except Poll.DoesNotExist:
raise Http404
return render(request, ' polls/detail.html ' , { ' poll ' : poll})
创建detail模板文件("polls/templates/polls/detail.html"):
<
h1
>
{{ poll.question }}
</
h1
>
< ul >
{% for choice in poll.choice_set.all %}
< li > {{ choice.choice_text }} </ li >
{% endfor %}
</ ul >
< ul >
{% for choice in poll.choice_set.all %}
< li > {{ choice.choice_text }} </ li >
{% endfor %}
</ ul >
方法简化:get_object_or_404()
使用该API简化模型与视图的耦合度。
from
django.shortcuts
import
render, get_object_or_404
from polls.models import Poll
def detail(request, poll_id):
poll = get_object_or_404(Poll, pk = poll_id)
return render(request, ' polls/detail.html ' , { ' poll ' : poll})
from polls.models import Poll
def detail(request, poll_id):
poll = get_object_or_404(Poll, pk = poll_id)
return render(request, ' polls/detail.html ' , { ' poll ' : poll})
5、除掉模板中url的硬编码
前者index模板中存在url硬编码,如果以后项目polls链接发生变动,则模板也要一起修改。
<
li
><
a
href
="/polls/{{ poll.id }}/"
>
{{ poll.question }}
</
a
></
li
>
使用模板语言的{% url %}标记可以消除这种问题。
<
li
><
a
href
="{% url 'detail' poll.id %}"
>
{{ poll.question }}
</
a
></
li
>
通过url标记,来调用urls.py("polls/urls.py")配置文件中取名为detail的url链接。
url(r
'
^(?P<poll_id>\d+)/$
'
, views.detail, name
=
'
detail
'
),
如果url有所变动,例如在原有基础上增加(“polls/specifics/12/”)
url(r
'
^specifics/(?P<poll_id>\d+)/$
'
, views.detail, name
=
'
detail
'
),
6、URL命名空间
项目存在多个应用时,不同应用之间url名字可能存在重复。给每个应用加上命名空间以避免命名冲突问题。
给项目的url配置文件("mysite/urls.py")加上命名空间:
from
django.conf.urls
import
patterns, include, url
from django.contrib import admin
admin.autodiscover()
urlpatterns = patterns( '' ,
url(r ' ^polls/ ' , include( ' polls.urls ' , namespace = " polls " )),
url(r ' ^admin/ ' , include(admin.site.urls)),
)
from django.contrib import admin
admin.autodiscover()
urlpatterns = patterns( '' ,
url(r ' ^polls/ ' , include( ' polls.urls ' , namespace = " polls " )),
url(r ' ^admin/ ' , include(admin.site.urls)),
)
index.html调用url标记时,加上命名空间前缀。
<
li
><
a
href
="{% url 'polls:detail' poll.id %}"
>
{{ poll.question }}
</
a
></
li
>