from functools import wraps
from django.dispatch import receiver
from django_fsm.signals import post_transition as post_transition_signal
__all__ = ["post_transition"]
"""
Implements post_transition decorator hooks for Django-FSM.
Usage:
@transition(field=state, source="abc", target="def)
def my_state_change(self):
# self.state hasn't updated yet!
assert self.state == "abc"
@post_transition(my_state_change):
def post_my_state_change(self):
# self.state has updated, but has not been saved
assert self.state == "def"
"""
_POST_TRANSITION_IDENTIFIER = "_fsm_post_transition"
def post_transition(transition_method):
"""
Links a post transition hook to the transition, so that our receiver can
identify the hook.
"""
def inner_function(func):
@wraps(func)
def _post_transition_hook(instance):
return func(instance)
setattr(transition_method, _POST_TRANSITION_IDENTIFIER, func.__name__)
return _post_transition_hook
return inner_function
@receiver(post_transition_signal)
def post_transition_handler(sender, instance, name, source, target, **kwargs):
"""
Identifies the hook linked to the transition method, and calls it with no
arguments.
The transition has **not** been saved at this point.
"""
transition_method = getattr(instance, name)
try:
post_hook_name = getattr(transition_method, _POST_TRANSITION_IDENTIFIER)
except AttributeError:
return
post_func = getattr(instance, post_hook_name)
post_func()
