Mixins¶

Your model can inherited from a custom mixin to auto-instantiate a state machine.

MachineMixin¶

class statemachine.mixins.MachineMixin(*args, **kwargs)[source]¶

This mixing allows a model to automatically instantiate and assign an StateMachine.

state_field_name: str = 'state'¶: The model’s state field name that will hold the state value.

state_machine_attr: str = 'statemachine'¶: Name of the model’s attribute that will hold the machine instance.

state_machine_name: str = None¶: A fully qualified name of the class, where it can be imported.

Mixins example¶

Given a statemachine definition:

>>> from statemachine import StateMachine, State

>>> from statemachine.mixins import MachineMixin

>>> class CampaignMachineWithKeys(StateMachine):
...     "A workflow machine"
...     draft = State('Draft', initial=True, value=1)
...     producing = State('Being produced', value=2)
...     closed = State('Closed', value=3)
...     cancelled = State('Cancelled', value=4)
...
...     add_job = draft.to.itself() | producing.to.itself()
...     produce = draft.to(producing)
...     deliver = producing.to(closed)
...     cancel = cancelled.from_(draft, producing)

It can be attached to a model using mixin and the full qualified name of the class.

Warning

On this example the state_machine_name is receiving a __main__ module due to the way autodoc works so we can have automated testes on the docs examples.

On your code, use the fully qualified path to the statemachine class.

>>> class MyModel(MachineMixin):
...     state_machine_name = '__main__.CampaignMachineWithKeys'
...
...     def __init__(self, **kwargs):
...         for k, v in kwargs.items():
...             setattr(self, k, v)
...         super(MyModel, self).__init__()
...
...     def __repr__(self):
...         return "{}({!r})".format(type(self).__name__, self.__dict__)

>>> model = MyModel(state=1)

>>> isinstance(model.statemachine, CampaignMachineWithKeys)
True

>>> model.state
1

>>> model.statemachine.current_state == model.statemachine.draft
True

>>> model.statemachine.cancel()

>>> model.state
4

>>> model.statemachine.current_state == model.statemachine.cancelled
True