"""
在web开发中, 你可能会遇到下面这种场景:
在用户完成某个操作后, 自动去执行一些后续的操作. 譬如用户完成修改密码后,你要发送一份确认邮件
观察者模式：观察者模式(Observer)完美的将观察者和被观察的对象分离开。
举个例子，用户界面可以作为一个观察者，业务数据是被观察者，
用户界面观察业务数据的变化，发现数据变化后，就显示在界面上
"""
"""学习网站https://simpleisbetterthancomplex.com/tutorial/2016/07/28/how-to-create-django-signals.html"""
"""两个重要的对象：Sender receiver
sender dispatch a signal, receiver receive signal and do something
sender 是一个object, receiver是一个方法，或者对象的方法
将sender和receiver关联起来是通过signal dispatchers, 即Signal.connect()方法来关联sender,receiver
"""
# post_save信号
""" 在mode对象执行save函数时，就会触发该信号"""
from django.contrib.auth.models import User
from django.db.models.signals import post_save
def save_profile(sender, instance, **kwargs):
instance.profile.save()
post_save.connect(save_profile, sender=User)
# save_profile是receiver，User是sender, post_save是signal, 上面代码可以理解成：当User对象执行save函数后，就会执行save_profile函数
# 如果去掉post_save.connect的sender参数，如： post_save.connect(save_profile)， 则就是任意一个model执行了save函数，都会调用save_profile函数
"""关联sender和receiver还可以通过@receiver装饰器来完成
def receiver(signal, **kwargs)"""
# 两个参数，signal可以是元组或者列表，或者单个信号
# **kwargs是位置参数，注意
from django.contrib.auth.models import User
from django.db.models.signals import post_save
from django.dispatch import receiver
@receiver(post_save, sender=User)
def save_profile(sender, instance, **kwargs):
instance.profile.save()
# 注册信号不应该在app的models或者根目录，django建议我们将signals放到config里面，以下面为了，profile为一个app；cmdbox是project
# profile/signals.py
from django.contrib.auth.models import User
from django.db.models.signals import post_save
from django.dispatch import receiver
from cmdbox.profiles.models import Profile
@receiver(post_save, sender=User)
def create_user_profile(sender, instance, created, **kwargs):
if created:
Profile.objects.create(user=instance)
@receiver(post_save, sender=User)
def save_user_profile(sender, instance, **kwargs):
instance.profile.save()
""" instance参数就是sender的实例化对象"""
#profiles/app.py:
from django.apps import AppConfig
from django.utils.translation import ugettext_lazy as _
class ProfilesConfig(AppConfig):
name = 'cmdbox.profiles'
verbose_name = _('profiles')
def ready(self):
import cmdbox.profiles.signals # noqa
# profiles/__init__.py: 如果已经在工程里面注册了app,这里是不需要的
default_app_config = 'cmdbox.profiles.apps.ProfilesConfig'
# 如果是通过connect关联sender和receiver,参考下面代码
# profile/signals.py
from cmdbox.profiles.models import Profile
def create_user_profile(sender, instance, created, **kwargs):
if created:
Profile.objects.create(user=instance)
def save_user_profile(sender, instance, **kwargs):
instance.profile.save()
# profile/app.py
from django.apps import AppConfig
from django.contrib.auth.models import User
from django.db.models.signals import post_save
from django.utils.translation import ugettext_lazy as _
from cmdbox.profiles.signals import create_user_profile, save_user_profile
class ProfilesConfig(AppConfig):
name = 'cmdbox.profiles'
verbose_name = _('profiles')
def ready(self):
post_save.connect(create_user_profile, sender=User)
post_save.connect(save_user_profile, sender=User)
# profiles/__init__.py:
default_app_config = 'cmdbox.profiles.apps.ProfilesConfig'
