Signals

Mocha uses Blinker to provide a fast dispatching system that allows any number of interested parties to subscribe to events, or “signals”.

As it will be described below, a best way to use signal is to dispatch data/message between modules.

For example, when a user register using the built-in AUTH, you may want to do something with that new user. So the create_user emit a signal containing the new user data, and each function observing the create_user, will be executed

Import

from mocha.decorators import emit_signal

Emit Signal

@emit_signal

A decorator that will turn a function into a signal emitter, which will contain a pre and post signal.

# signals.py
from mocha import decorators as deco

@deco.emit_signal
def do_something(data):
    return data

The example above creates a signal do_something, each time this function is invoked it will emit two signals do_something.pre and do_something.post. These objects (pre, post) were created when @emit_signal decorated the do_something function.

pre will be invoked before running accepting the signal, and post after the signal is executed.

For every @emit_signal use, the function will have two blinker signal objects: pre and post

@emit_signal
def hello():
    pass

will now have the following decorators:

@hello.post
@hello.pre

Receive Signal

@observe

@observe allows you to connect a function to an emitter. @observe is a shortcut for @post.connect.

import my_signals

@signals.do_something.observe
def my_thing(result, **kw):
    if result:
        pass

To fully utilize Blinker functionalities, use post and pre, for example @do_something.post.connect, @do_something.pre.connect

@post.connect

@signals.do_something.post.connect
def receive_create_user(user, **kw):
    if user:
        # do something with user

The function receiving the signal, must have 2 args:

• result: that's the result sent from the signal
• **kwargs: some
  • kwargs: kwargs that were passed in the signal function
  • sender: The name of the function
  • emitter: The instance of the

@pre.connect

@signals.do_something.pre.connect
def receive_create_user_pre(**kw):
    # do something