django之信号

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。

1、Django内置信号

Model signals

    pre_init                    # django的modal执行其构造方法前，自动触发

    post_init                   # django的modal执行其构造方法后，自动触发

    pre_save                    # django的modal对象保存前，自动触发

    post_save                   # django的modal对象保存后，自动触发

    pre_delete                  # django的modal对象删除前，自动触发

    post_delete                 # django的modal对象删除后，自动触发

    m2m_changed                 # django的modal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：

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

    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

from django.core.signals import request_finished
from django.dispatch import receiver

@receiver(request_finished)
def my_callback(sender, **kwargs):
    print("Request finished!")

from django.core.signals import request_finished
from django.dispatch import receiver

@receiver(request_finished)
def my_callback(sender, **kwargs):
    print("Request finished!")

2、自定义信号

a. 定义信号

import django.dispatch

pizza_done = django.dispatch.Signal(providing_args=["toppings", "size"])

b. 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。

更多，https://docs.djangoproject.com/en/dev/topics/signals/