场景

我们有2个页面 ,一个是文章显示页面,一个是文章增加页面, 文章只有title,content及is_public三个域.

我们使用signal是完成,当用户添加一个文章后,我们置其is_public=False, 我们使用signal来实现此功能.

注册signal

下面是测试用的project的文件结构,具体可以 下载源代码 来在本地运行.

.
|-- __init__.py
|-- __init__.pyc
|-- logs
| `-- filelog.log
|-- manage.py
|-- settings.py
|-- settings.pyc
|-- signal.db
|-- testsignal
| |-- __init__.py
| |-- __init__.pyc
| |-- models.py
| |-- models.pyc
| |-- signals.py
| |-- signals.pyc
| |-- templates
| | |-- add.html
| | |-- base.html
| | `-- index.html
| |-- tests.py
| |-- urls.py
| |-- urls.pyc
| |-- views.py
| `-- views.pyc
|-- urls.py
`-- urls.pyc

testsignal是我们建立的示例app, 我们首先要注册signal, 具体代码如下(testsignal/signals.py):

import django.dispatch
delete_done = django.dispatch.Signal(providing_args=['obj'])

引入django的包, 并且注册 delete_done为我们将要使用的signal.

关联signal对应的listener

然后我们关联对应的listener, 代码如下: (testsignal/models.py)

from django.db.models.signals import pre_save
from django.db import models
import logging
import signals
# Create your models here.
class Article(models.Model):
title = models.CharField(max_length=200)
content = models.TextField()
is_public = models.BooleanField(default=True, blank=True)
def delete(self):
#self.is_public = False
signals.delete_done.send(sender=Article, obj=self)
def __unicode__(self):
return self.title
def zhutao(sender, kwargs):
logging.debug(kwargs)
if "obj" in kwargs:
obj = kwargs.get("obj")
logging.debug(obj.is_public)
obj.is_public = False
obj.save()
logging.debug("signal recieved! zhutao is called.")
logging.debug(obj.is_public)
signals.delete_done.connect(zhutao, sender=Article)

我们来看最后一行, signals.delete_done.connect(zhutao, sender=Article), 即将 我们上面注册的 delete_done 和 监听函数 zhutao 关联了起来, 而 这里的 sender=Article, 则是用来限制只有当Article有更新时我们才会触发这个事件.

触发监听事件

最后,我们要在特定操作发生时触发相应的监听函数, 具体代码如下(testsignal/views.py):

from django.http import HttpResponse,HttpResponseRedirect
from django.core.urlresolvers import reverse
from django.shortcuts import render_to_response
import signals
from models import *
def index(request):
articles = Article.objects.all().order_by("-id")
return render_to_response("index.html", {"articles":articles})
def add(request):
if request.method == "POST":
title = request.POST.get("title", "")
content = request.POST.get("content", "")
if title and content:
article = Article(title=title, content=content)
article.save()
article.delete()
return HttpResponseRedirect(reverse(index))
return render_to_response("add.html", {})

其它的只是django的普通views.py中的方法,我们主要来看 article.delete() 这行代码, 执行这个后,我们会调用models.py中的delete方法,见上面的models.py中的代码, 它会执行下面一行代码:

signals.delete_done.send(sender=Article, obj=self)

面这行代码正是向delete_done发送了事件的触发,此时,对应的监听函数 zhutao 会得到执行,

从而将 is_public 置为False.

我们的任务也得以完成.

具体的说明可以 下载源代码 来运行,你会在logs/filelog.log文件中看到对应的log输出.

示例输出为:

2009-10-27 03:28:27,202 DEBUG models.zhutao Line:26 {'signal': <django.dispatch.dispatcher.Signal object at 0x9523e4c>, 'obj': <Article: aaa>}
2009-10-27 03:28:27,203 DEBUG models.zhutao Line:29 True
2009-10-27 03:28:27,209 DEBUG models.zhutao Line:32 signal recieved! zhutao is called.
2009-10-27 03:28:27,209 DEBUG models.zhutao Line:33 False