• django -- 信号


    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)
    __init__.py

    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()})
    View Code

    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
    View Code
    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
    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):
        ...
    指定发送者

    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/

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  • 原文地址:https://www.cnblogs.com/robertx/p/11087197.html
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