django的 信号

1、信号，其实就是钩子，可以在上面几种情况下定义执行某个函数，我们一般在project的__init__文件中定义，下面就是一个例子

2、用到模块需要导入，分别在下面的几个路径中

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
from django.db.models.signals import post_init

from django.db.models.signals import pre_save
from django.db.models.signals import post_save

from django.db.models.signals import pre_delete
from django.db.models.signals import post_delete

from django.db.models.signals import m2m_changed
from django.db.models.signals import pre_migrate
from django.db.models.signals import post_migrate

from django.test.signals import setting_changed
from django.test.signals import template_rendered

from django.db.backends.signals import connection_created

　　

3、下面就是一个使用的例子，把函数注册到信号中

# 1、定义执行的函数
def callback1(sender,**kwargs):
    print("before pre_migrate")
    print(sender,kwargs)

# 定义执行的函数
def callback2(sender,**kwargs):
    print("after pre_migrate")
    print(sender,kwargs)

# 在执行migrate之前会执行的函数
pre_migrate.connect(callback1)

# 在执行migrate之后执行的函数
post_migrate.connect(callback2)

　　

4、下面我们执行migrate命令就会有下面提示

E:\python\django_last>python manage.py migrate
Operations to perform:
  Apply all migrations: admin, app1, auth, contenttypes, sessions
before pre_migrate
<AdminConfig: admin> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C755D0>, 'app_config': <AdminConfig: admin>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.db.migrations
.state.StateApps object at 0x02CF1130>, 'plan': []}
before pre_migrate
<AuthConfig: auth> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C755D0>, 'app_config': <AuthConfig: auth>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.db.migrations.sta
te.StateApps object at 0x02CF1130>, 'plan': []}
before pre_migrate
<ContentTypesConfig: contenttypes> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C755D0>, 'app_config': <ContentTypesConfig: contenttypes>, 'verbosity': 1, 'interactive': True, 'using': 'default', '
apps': <django.db.migrations.state.StateApps object at 0x02CF1130>, 'plan': []}
before pre_migrate
<SessionsConfig: sessions> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C755D0>, 'app_config': <SessionsConfig: sessions>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.d
b.migrations.state.StateApps object at 0x02CF1130>, 'plan': []}
before pre_migrate
<App1Config: app1> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C755D0>, 'app_config': <App1Config: app1>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.db.migrations.sta
te.StateApps object at 0x02CF1130>, 'plan': []}
Running migrations:
  No migrations to apply.
after pre_migrate
<AdminConfig: admin> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C75610>, 'app_config': <AdminConfig: admin>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.db.migrations
.state.StateApps object at 0x03183FD0>, 'plan': []}
after pre_migrate
<AuthConfig: auth> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C75610>, 'app_config': <AuthConfig: auth>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.db.migrations.sta
te.StateApps object at 0x03183FD0>, 'plan': []}
after pre_migrate
<ContentTypesConfig: contenttypes> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C75610>, 'app_config': <ContentTypesConfig: contenttypes>, 'verbosity': 1, 'interactive': True, 'using': 'default', '
apps': <django.db.migrations.state.StateApps object at 0x03183FD0>, 'plan': []}
after pre_migrate
<SessionsConfig: sessions> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C75610>, 'app_config': <SessionsConfig: sessions>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.d
b.migrations.state.StateApps object at 0x03183FD0>, 'plan': []}
after pre_migrate
<App1Config: app1> {'signal': <django.dispatch.dispatcher.Signal object at 0x01C75610>, 'app_config': <App1Config: app1>, 'verbosity': 1, 'interactive': True, 'using': 'default', 'apps': <django.db.migrations.sta
te.StateApps object at 0x03183FD0>, 'plan': []}

E:\python\django_last>

　　

上面是python给我们定义的信号，我们还可以自定义信号，下面说一下如何自定义信号，也是写在projec的__init__文件中

1、注册我们的信号，和信号的里的函数

# 1、导入模块
import django.dispatch

# 2、注册一个信号
test = django.dispatch.Signal(providing_args=["aa","bb"])

# 这里的aa和bb相当于形参

# 3、定义一个触发信号要执行的函数
def callback3(sender,**kwargs):
    print("自定义信号")
    print(sender,kwargs)

# 4、给信号注册一个函数
test.connect(callback3)

　　

2、在函数使用自定义的信号

# 使用我们自定义的信号
def cus_signal(request):

    # 导入自定义的信号,这里需要注意，导入__init__下的信号，直接用下面的方式就可以了
    from django_last import test

    # 触发信号，这里要记得要传参数,sender的意思是 谁发送的信号
    test.send(sender="自定义信号",aa="django",bb="python")
    return HttpResponse("自定义信号")

　　

3、效果如下

无论是django定义的信号，还是我们自定义的信号，我们就可以为一个信号注册多个函数，这些多个函数会按照注册的顺序执行