信号
新增数据的数据的时候写一条日志可以用到信号
Django中提供了“信号调度”,用于在框架执行操作时解耦。通俗来讲,就是一些动作发生的时候,信号允许特定的发送者去提醒一些接受者。
使用:
1. 在项目下的__init__文件中
from django.core.signals import request_finished from django.core.signals import request_started from django.core.signals import got_request_exception from django.db.models.signals import class_prepared from django.db.models.signals import pre_init, post_init from django.db.models.signals import pre_save, post_save from django.db.models.signals import pre_delete, post_delete from django.db.models.signals import m2m_changed from django.db.models.signals import pre_migrate, post_migrate from django.test.signals import setting_changed from django.test.signals import template_rendered def callback(sender,**kwargs): print('xxxxx') print(sender) print(kwargs) def callback1(sender,**kwargs): print('111') print(sender) print(kwargs) # post_save.connect(callback) # post_save.connect(callback1)
2.视图函数中执行的操作会触发信号的回调函数
def index(request, *args): # models.Student.objects.create(name='alex') obj = models.Student.objects.get(pk=5) print(obj) obj.name = '222' obj.save() obj = models.Student.objects.create(name='alex',classes_id=1) return render(request, 'index.html',{'time':time.time()})
讲解:
1、Django内置信号
Model signals pre_init # django的model执行其构造方法前,自动触发 post_init # django的model执行其构造方法后,自动触发 pre_save # django的model对象保存前,自动触发 post_save # django的model对象保存后,自动触发 pre_delete # django的model对象删除前,自动触发 post_delete # django的model对象删除后,自动触发 m2m_changed # django的model中使用m2m字段操作第三张表(add,remove,clear)前后,自动触发 class_prepared # 程序启动时,检测已注册的app中modal类,对于每一个类,自动触发 Management signals pre_migrate # 执行migrate命令前,自动触发 post_migrate # 执行migrate命令后,自动触发 Request/response signals request_started # 请求到来前,自动触发 request_finished # 请求结束后,自动触发 got_request_exception # 请求异常后,自动触发 Test signals setting_changed # 使用test测试修改配置文件时,自动触发 template_rendered # 使用test测试渲染模板时,自动触发 Database Wrappers connection_created # 创建数据库连接时,自动触发
对于Django内置的信号,仅需注册指定信号,当程序执行相应操作时,自动触发注册函数:
注册信号,写入与project同名的文件夹下的_init_.py文件中,也是换数据库引擎的地方。
from django.core.signals import request_finished from django.core.signals import request_started from django.core.signals import got_request_exception from django.db.models.signals import class_prepared from django.db.models.signals import pre_init, post_init from django.db.models.signals import pre_save, post_save from django.db.models.signals import pre_delete, post_delete from django.db.models.signals import m2m_changed from django.db.models.signals import pre_migrate, post_migrate from django.test.signals import setting_changed from django.test.signals import template_rendered from django.db.backends.signals import connection_created def callback(sender, **kwargs): print("xxoo_callback") print(sender,kwargs) xxoo.connect(callback) # xxoo指上述导入的内容
def my_callback(sender, **kwargs): print("Request finished!") # 方法一: from django.core.signals import request_finished request_finished.connect(my_callback) # 方法二: from django.core.signals import request_finished from django.dispatch import receiver @receiver(request_finished) def my_callback(sender, **kwargs): print("Request finished!") 示例
from django.db.models.signals import pre_save from django.dispatch import receiver from myapp.models import MyModel @receiver(pre_save, sender=MyModel) def my_handler(sender, **kwargs): ...
2、自定义信号
a. 定义信号
在某py文件中定义信号。
import django.dispatch pizza_done = django.dispatch.Signal(providing_args=["toppings", "size"])
b. 注册信号
在_init_.py 中注册信号
def callback(sender, **kwargs): print("callback") print(sender,kwargs) pizza_done.connect(callback)
c. 触发信号
from 路径 import pizza_done pizza_done.send(sender='seven',toppings=123, size=456)
由于内置信号的触发者已经集成到Django中,所以其会自动调用,而对于自定义信号则需要开发者在任意位置触发。
官方文档对信号的描述: https://docs.djangoproject.com/en/1.11/topics/signals/