django signal 浅析

默认的signals极其参数

（django 1.6.5)

模型的（django/db/models/signal.py）：

from django.dispatch import Signal

class_prepared = Signal(providing_args=["class"])

pre_init = Signal(providing_args=["instance", "args", "kwargs"], use_caching=True)
post_init = Signal(providing_args=["instance"], use_caching=True)

pre_save = Signal(providing_args=["instance", "raw", "using", "update_fields"],
                 use_caching=True)
post_save = Signal(providing_args=["instance", "raw", "created", "using", "update_fields"], use_caching=True)

pre_delete = Signal(providing_args=["instance", "using"], use_caching=True)
post_delete = Signal(providing_args=["instance", "using"], use_caching=True)

pre_syncdb = Signal(providing_args=["app", "create_models", "verbosity", "interactive", "db"])
post_syncdb = Signal(providing_args=["class", "app", "created_models", "verbosity", "interactive", "db"])

m2m_changed = Signal(providing_args=["action", "instance", "reverse", "model", "pk_set", "using"], use_caching=True)

用户登录的(django/contrib/auth/signals.py)

from django.dispatch import Signal

user_logged_in = Signal(providing_args=['request', 'user'])
user_login_failed = Signal(providing_args=['credentials'])
user_logged_out = Signal(providing_args=['request', 'user'])

关于request请求的(django/core/signals.py)

from django.dispatch import Signal

request_started = Signal()
request_finished = Signal()
got_request_exception = Signal(providing_args=["request"])

　

数据库连接的(django/db/backends/signals.py)

from django.dispatch import Signal

connection_created = Signal(providing_args=["connection"])

原理

简图

Signal类和receiver修饰符位于 django/dispatch/dispatcher.py中。

关于模型的signals的触发实际看django/db/modes/base.py 中的Model类，例如 post_save（579~582）如下：

# Signal that the save is complete
        if not meta.auto_created:
            signals.post_save.send(sender=origin, instance=self, created=(not updated),
                                   update_fields=update_fields, raw=raw, using=using)

　

小结

1. 实际上signals的设计是一个很松的耦合的设计。

可以说， post_save和save没有半毛钱的关系，如果你在save的最后代码里触发它，它名副其实。

当然你也可以在其他任意的层级，任意位置触发它。

2. 本质上讲， 就是一个 list of function, 然后这个list有一个名字， 然后你可以在任意位置，任意时机调用list中的function.

3. 触发对象，如果在修饰function的时候有传参数sender，则只有此类型的实例才能够触发该signal

转载请注明本文来自：http://www.cnblogs.com/Tommy-Yu/p/4101575.html，谢谢！