Django中提供了“信號調度”，用於在框架執行操作時解耦。通俗來講，就是一些動作發生的時候，信號允許特定的發送者去提醒一些接受者

1、Django內置信號

Model signals
    pre_init                    # django的modal執行其構造方法前，自動觸發
    post_init                   # django的modal執行其構造方法後，自動觸發
    pre_save                    # django的modal對象保存前，自動觸發
    post_save                   #
 
 django的modal對象保存後，自動觸發
    pre_delete                  # django的modal對象刪除前，自動觸發
    post_delete                 # django的modal對象刪除後，自動觸發
    m2m_changed                 # django的modal中使用m2m字段操作第三張表（add,remove,clear）前後，自動觸發
    class_prepared              # 程序啟動時，檢測已註冊的app中modal類，對於每一個類，自動觸發
Management signals
    pre_migrate                 
 
# 執行migrate命令前，自動觸發
    post_migrate                # 執行migrate命令後，自動觸發
Request/response signals
    request_started             # 請求到來前，自動觸發
    request_finished            # 請求結束後，自動觸發
    got_request_exception       # 請求異常後，自動觸發
Test signals
    setting_changed             # 使用test測試修改配置文件時，自動觸發
    template_rendered           #
 
 使用test測試渲染模板時，自動觸發
Database Wrappers
    connection_created          # 創建數據庫連接時，自動觸發

這個信號 django內部已經全部定死 已經埋下觸發信號操作

於Django內置的信號，僅需註冊指定信號，當程序執行相應操作時，自動觸發註冊函數：

要註冊 先導入

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指上述導入的內容

xxoo是什麽 比如

.connect() 裏面 傳的 是一個自定義函數 代表在信號裏面 註冊一個函數

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 f1(sender, **kwargs):
    print("end")


pre_init.connect(f1)

也可以註冊多個函數 按照順序執行

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 f1(sender, **kwargs):
    print("end")

def f2(sender, **kwargs):
    print("end22")

pre_init.connect(f1)
pre_init.connect(f2)

想在django 應用 註冊的函數的 信號註冊到django

在django項目 創建一個sg.py 文件

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 f1(sender, **kwargs):
    print("xxoo")


pre_init.connect(f1)

django執行 models構造方法前 自動觸發信號

在django項目中的 __init__.py 文件 導入 sg.py 模塊 那就django程序一運行，自動把sg.py 代碼加載到內存，然後相應信號函數就註冊了

urls.py signal函數

from django.conf.urls import url
from django.contrib import admin
from django.conf.urls import include
from app01 import views

urlpatterns = [
    # url(r‘^admin/‘, admin.site.urls),
    url(r‘^login/‘, views.login),
    url(r‘^index/‘, views.index),
    url(r‘^logout/‘, views.logout),
    url(r‘^test/‘, views.test),
    url(r‘^cache/‘, views.cache),
    url(r‘^signal/‘, views.signal),
]

views.py signal函數 用來測試註冊的信號

def signal(request):

    from app01 import models

    obj = models.UserInfo(username=‘mike‘)
    print("end")
    obj.save()

    obj = models.UserInfo(username=‘mike‘)
    print("end1")
    obj.save()

    obj = models.UserInfo(username=‘mike‘)
    print("end2")
    obj.save()

    return HttpResponse("ok")

一啟動django 註冊的函數馬上加載到內存了

xxoo
xxoo
System check identified no issues (0 silenced).
January 07, 2019 - 17:17:06
Django version 1.11, using settings ‘day21django.settings‘
Starting development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK

執行django signal url

後臺拿到信息

每一次 執行 models構造方法前 自動觸發信號 函數 然後打印信息

mike
jack
tom
小張
小剛
老張
xxoo
end
xxoo
end1
xxoo
end2
xiaogang
xiaoming
peter
[07/Jan/2019 17:25:01] "GET /signal/ HTTP/1.1" 200 2

django 信號介紹 1.11