python FSM Fysom callbacks on the other way

I am using Fysom to create FSM. I want to use callbacks in an other way:

TABLE = {
'initial': 'OFF',
'events': [{'name': 'load', 'src': 'OFF', 'dst': 'LOADED'},],
'callbacks': {'onload': myfunction,}}

fsm = Fysom(TABLE)

Here if I launch fsm.onload() it will execute myfunction. Instead I want If I launch myfunction() it will lunch fsm.onload().

I took a look on the script and related part is here:

def _enter_state(self, e):
    '''
        Executes the callback for onenter_state_ or on_state_.
    '''
    for fnname in ['onenter' + e.dst, 'on' + e.dst]:
        if hasattr(self, fnname):
            return getattr(self, fnname)(e)

I don't see how to change this peace of code for my purpose.

Solution

You cannot implement callbacks "in the other direction" without touching myfunction. A callback is actually an inverted call (hollywood principle), so the inverse of a callback is a simple call.

What this means is that myfunction should call the state machine transition directly. As a consequence, the state machine object must be in the scope of myfunction.

At this point you have some possibilities for implementation :

Have myfunction be a closure :

def outer():
    fsm = Fysom(TABLE)
    def myfunction():
        print("I call the state machine transition when called")
        fsm.onload()
    return fsm

Use a global state machine or scope it in a class :

class Foo(object):

    def __init__(self):
        self.fsm = Fysom(TABLE)

    def my_method(self):
        self.fsm.onload()

Create a decorator that calls the state transition method before/after executing the function. Then decorate away with
```
fsm = Fysom(TABLE)

@transition(fsm, "onload")
def myfunction():
    pass
```
Note that this also requires fsm to be defined in this scope.