Django's built-in signal

Pre_init   automatically triggered before the model executes the construction method
Post_init  Django model is automatically triggered after the construction method is executed
Pre_save  Django objects are automatically triggered before they are saved
Post_save  Django objects are automatically triggered after they are saved
Pre_delete  This is a Django object that is automatically triggered before it is deleted
Post_delete  Django objects are automatically triggered after they are deleted
M2m_changed   automatically triggers before and after using the third sheet (add,remove,clear)
Class_prepared when the program starts, the table for the registered app, automatically triggers for each class

Management Signals
Pre_migrate   automatically triggered before executing the migrate command
Post_migrate    automatically triggers after executing the migrate command

Request/response  Signals
  auto-Trigger before request_started request arrives
  auto-Trigger after request_finished request ends


Test Signals
Settings_chnaged    automatically triggers when a configuration file is tested using test
settings_rendered   Using Test render template Yes, auto trigger

DATABSE   Signals
Connections_created  This is when the database is created, it automatically triggers


For Django's built-in signal, you only need to register the corresponding signal (register in __init__ under Project), and it will automatically trigger when the program executes.

Project_singal below the __init__ inside:

########################### #在这里面可以添加这个信号量

From   django.db.models   import  signals
############################## #导入这个信号量的模块
Print (' operation to perform the semaphore of this Singal ')

########### #这个是一开始就会执行的操作
def before_save (*args,**kwargs):
    Print (' Printing out ', Args,kwargs)

Signals.pre_save.connect (Before_save)
####################################################################################

Results of execution:

‘‘‘
() {' Signal ': <django.db.models.signals.modelsignal object at 0x0000022947a93080>, ' sender ': <class ' App01.models.Booke ', ' instance ': <booke:booke object (None), ' raw ': False, ' using ': ' Default ', ' Update_ Fields ': None}

‘‘‘
#//This will promise this log out


Views

From app01.models Import *

From django.shortcuts import HttpResponse

def  Action (requets):
    Print (' Start executing this fun3 function ')
    Models. User.objects.filter (id=1). Update (user_name= ' Yun ') # #这个是可以更新这个数据进去
    Models. Book.objects.create (book_name= ' Jane Eyre ') ############## #这个是创建这个数据进去
    Print (' Create successful ')
    return  HttpResponse (' Fun3 ')

Models
Class book  (models. Model):

Book_name=models. Charfield (max_length=32,verbose_name= ' book name ')

Class  User (models. Model):

User_name=models. Username (MAX_LENGTH=32)

Django's built-in signal