0x01 消息机制

消息机制，从字面理解，通过传递消息来触发某些事件。第一次接触到的时候，让我想到的是win的消息触发机制。在Python中，blinker主要用于解耦模块，使得代码逻辑更加清晰，其他作用我还没接触到，有待开发。
比如登陆逻辑，通常情况下像这个样子：

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def login():
	...	
	do_something()
    return

如果加上验证逻辑和日志，代码可能会变得更加复杂，变成这个样子：

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def login():
	...
    check()
    log()
    do_something()
    return

慢慢的登陆逻辑就变得很繁琐，这时候就可以使用blinker来解耦登陆逻辑。

0x02简单的例子

在栗子中学习，首先看下基本的触发

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from blinker import signal

def subscriber(sender):
    print("Got a signal sent by %r" % sender)
    pass

ready = signal('ready')
ready.connect(subscriber)

class Process(object):
    def __init__(self, name):
        self.name = name

    def go(self):
        ready = signal('ready')
        ready.send(self)
        print('processing %s'%self.name)
        #complete = signal('complete')
        #complete.send(self)

    def __repr__(self):
        return "<Process %s>"% self.name

if __name__=="__main__":
	process_a = Process('a')
    process_a.go()


--------------------------------------------------------------
python.exe test.py
Got a signal sent by <Process a>
processing a

Process finished with exit code 0

从blinker引入一个signal类，生成了一个“ready”的信号，并使用connect方法将这个信号实例与subscriber方法绑定。之后在Process类中，生成了一个相同名字的信号，根据blinker的机制，这两个信号是同一个实例，也就是说，signal使用的是单例模式。然后使用ready的send方法放出信号，这时候与ready信号绑定的subscriber方法触发，输出“Got a signal sent by ”，之后输出“processing a”。

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from blinker import signal

def subscriber(sender):
    print("Got a signal sent by %r" % sender)
    pass

ready = signal('ready')
ready.connect(subscriber)

def subcomplete(sender):
    print("complete a signal sent by %r"% sender)
    pass
complete = signal('complete')
complete.connect(subcomplete)

class Process(object):
    def __init__(self, name):
        self.name = name

    def go(self):
        ready = signal('ready')
        ready.send(self)
        print('processing %s'%self.name)
        complete = signal('complete')
        complete.send(self)

    def __repr__(self):
        return "<Process %s>"% self.name

def b_subscriber(sender):
    print("Caught the signal from process_b")
    assert sender.name == 'b'

if __name__=="__main__":
    
    process_b = Process('b')
    ready.connect(b_subscriber,sender=process_b)
    process_b.go()
    process_a = Process('a')
    process_a.go()
    print(ready.receivers)
    
------------------------------------------------------------------------
Got a signal sent by <Process b>
Caught the signal from process_b
processing b
complete a signal sent by <Process b>
Got a signal sent by <Process a>
processing a
complete a signal sent by <Process a>
{6061864: <weakref at 0x00000000010F80A8; to 'function' at 0x00000000005C7F28 (subscriber)>, 11257784: <weakref at 0x000000000111FA68; to 'function' at 0x0000000000ABC7B8 (b_subscriber)>}


Process finished with exit code 0

重新绑定一个信号，将b_subscriber方法与process_b绑定，这时候ready的队列里有两个方法，并会依次触发，得到上面的输出效果。

0x03 End

作为flask中的订阅信号，其功能十分强大。