Django integration¶
import fsm
from django.db import models
class MyModel(models.Model, fsm.FiniteStateMachineMixin):
"""An example to test the state machine.
Contains transitions to everywhere, nowhere and specific states.
"""
CHOICES = (
('created', 'CREATED'),
('pending', 'PENDING'),
('running', 'RUNNING'),
('success', 'SUCCESS'),
('failed', 'FAILED'),
('retry', 'RETRY'),
)
state_machine = {
'created': '__all__',
'pending': ('running',),
'running': ('success', 'failed'),
'success': None,
'failed': ('retry',),
'retry': ('pending', 'retry'),
}
state = models.CharField(max_length=30, choices=CHOICES, default='created')
def on_change_state(self, previous_state, next_state, **kwargs):
self.save()
Django Rest Framework¶
If you are using serializers
, they usually perform the save
, so saving inside on_change_state
is not necessary.
One simple solution is to do this:
class MySerializer(serializers.ModelSerializer):
def update(self, instance, validated_data):
new_state = validated_data.get('state', instance.state)
try:
instance.change_state(new_state)
except fsm.InvalidTransition:
raise serializers.ValidationError("Invalid transition")
instance = super().update(instance, validated_data)
return instance