decev 0.0.1

Event handlers with decorators

DECEV (decorator events) by @dantechguy

A teeny library for event handling which uses decorators for event subscription

Usage

1. Create an EventHandler object and events

import decev
# pass list of event names
events = decev.EventHandler(['firstEvent', 'event_two', 'LAST_EVENT'])

2. Add functions to events

Event functions cannot have any arguments

# add myFunction to firstEvent
@events.firstEvent
def myFunction():
    print('myFunction')

# add myOtherFunction to firstEvent and event_two
@events.firstEvent
@events.event_two
def myOtherFunction():
    print('myOtherFunction')

3. Add methods to events

Methods can only have the self argument

class MyClass:
    def __init__(self):
        # this must be run for methods to be subscribed
        events.subscribe_tagged_methods(self)

    # add myMethod to LAST_EVENT
    @events.LAST_EVENT
    def myMethod(self):
        print('myMethod')

# create instance of class        
myObject = MyClass()

4. Run events

events.run('firstEvent')
print()
events.run('event_two')
print()
events.run('LAST_EVENT')

Which produces this:

> py main.py
myOtherFunction
myFunction

myOtherFunction

myMethod

How it works

Any functions added with zero arguments are assumed to be regular functions, and are subscribed immediately to the event.

Any functions added with one argument are assumed to be methods (the argument being self), and are tagged with the corresponding event. Later, when subscribe_tagged_methods is called, all tagged methods are then subscribed to the event.

The reason we tag then subscribe for methods is because when the function would usually be subscribed, there is no value for self (there isn't an instance), so the method is unbound. Only once an instance has been created, we run subscribe_tagged_methods in its __init__ to successfully subscribe all methods now that there is a value for self.