Django friendly finite state machine support.
Project description
Django friendly finite state machine support
============================================
django-fsm adds declarative states management for django models.
Instead of adding some state field to a django model, and manage it
values by hand, you could use FSMState field and mark model methods
with the `transition` decorator. Your method will contain the side-effects
of the state change.
The decorator also takes a list of conditions, all of which must be met
before a transition is allowed.
Installation
------------
$ pip install django-fsm
Or, for the latest git version
$ pip install -e git://github.com/kmmbvnr/django-fsm.git#egg=django-fsm
Usage
-----
Add FSMState field to your model
from django_fsm.db.fields import FSMField, transition
class BlogPost(models.Model):
state = FSMField(default='new')
Use the `transition` decorator to annotate model methods
@transition(source='new', target='published')
def publish(self):
"""
This function may contain side-effects,
like updating caches, notifying users, etc.
The return value will be discarded.
"""
`source` parameter accepts a list of states, or an individual state.
You can use `*` for source, to allow switching to `target` from any state.
If calling publish() succeeds without raising an exception, the state field
will be changed, but not written to the database.
from django_fsm.db.fields import can_proceed
def publish_view(request, post_id):
post = get_object__or_404(BlogPost, pk=post_id)
if not can_proceed(post.publish):
raise Http404;
post.publish()
post.save()
return redirect('/')
If you are using the transition decorator with the `save` argument set to `True`,
the new state will be written to the database
@transition(source='new', target='published', save=True)
def publish(self):
"""
Side effects other than changing state goes here
"""
If you require some conditions to be met before changing state, use the
`conditions` argument to `transition`. `conditions` must be a list of functions
that takes one argument, the model instance. The function must return either
`True` or `False` or a value that evaluates to `True` or `False`. If all
functions return `True`, all conditions are considered to be met and transition
is allowed to happen. If one of the functions return `False`, the transition
will not happen. These functions should not have any side effects.
You can use ordinary functions
def can_publish(instance):
# No publishing after 17 hours
if datetime.datetime.now().hour > 17:
return False
return True
Or model methods
def can_destroy(self):
return self.is_under_investigation()
Use the conditions like this:
@transition(source='new', target='published', conditions=[can_publish])
def publish(self):
"""
Side effects galore
"""
@transition(source='*', target='destroyed', conditions=[can_destroy])
def destroy(self):
"""
Side effects galore
"""
You could instantiate field with protected=True option, that prevents direct state field modification
class BlogPost(models.Model):
state = FSMField(default='new', protected=True)
model = BlogPost()
model.state = 'invalid' # Raises AttributeError
### get_available_FIELD_transitions
You could specify FSMField explicitly in transition decorator.
class BlogPost(models.Model):
state = FSMField(default='new')
@transition(field=state, source='new', target='published')
def publish(self):
pass
This allows django_fsm to contribute to model class get_available_FIELD_transitions method,
that returns list of (target_state, method) available from current model state
### Foreign Key constraints support
If you store the states in the db table you could use FSMKeyField to
ensure Foreign Key database integrity.
### Signals
`django_fsm.signals.pre_transition` and `django_fsm.signals.post_transition` are called before
and after allowed transition. No signals on invalid transition are called.
Arguments sent with these signals:
**sender**
The model class.
**instance**
The actual instance being procceed
**name**
Transition name
**source**
Source model state
**target**
Target model state
### Drawing transitions
Renders a graphical overview of your models states transitions
# Create a dot file
$ ./manage.py graph_transitions -a > transitions.dot
# Create a PNG image file only for specific model
$ ./manage.py graph_transitions -o blog_transitions.png myapp.Blog
Changelog
---------
django 1.4.0 2011-12-21
* Add graph_transition command fro drawing state transition picture
django-fsm 1.3.0 2011-07-28
* Add direct field modification protection
django-fsm 1.2.0 2011-03-23
* Add pre_transition and post_transition signals
django-fsm 1.1.0 2011-02-22
* Add support for transition conditions
* Allow multiple FSMField in one model
* Contribute get_available_FIELD_transitions for model class
django-fsm 1.0.0 2010-10-12
* Initial public release
============================================
django-fsm adds declarative states management for django models.
Instead of adding some state field to a django model, and manage it
values by hand, you could use FSMState field and mark model methods
with the `transition` decorator. Your method will contain the side-effects
of the state change.
The decorator also takes a list of conditions, all of which must be met
before a transition is allowed.
Installation
------------
$ pip install django-fsm
Or, for the latest git version
$ pip install -e git://github.com/kmmbvnr/django-fsm.git#egg=django-fsm
Usage
-----
Add FSMState field to your model
from django_fsm.db.fields import FSMField, transition
class BlogPost(models.Model):
state = FSMField(default='new')
Use the `transition` decorator to annotate model methods
@transition(source='new', target='published')
def publish(self):
"""
This function may contain side-effects,
like updating caches, notifying users, etc.
The return value will be discarded.
"""
`source` parameter accepts a list of states, or an individual state.
You can use `*` for source, to allow switching to `target` from any state.
If calling publish() succeeds without raising an exception, the state field
will be changed, but not written to the database.
from django_fsm.db.fields import can_proceed
def publish_view(request, post_id):
post = get_object__or_404(BlogPost, pk=post_id)
if not can_proceed(post.publish):
raise Http404;
post.publish()
post.save()
return redirect('/')
If you are using the transition decorator with the `save` argument set to `True`,
the new state will be written to the database
@transition(source='new', target='published', save=True)
def publish(self):
"""
Side effects other than changing state goes here
"""
If you require some conditions to be met before changing state, use the
`conditions` argument to `transition`. `conditions` must be a list of functions
that takes one argument, the model instance. The function must return either
`True` or `False` or a value that evaluates to `True` or `False`. If all
functions return `True`, all conditions are considered to be met and transition
is allowed to happen. If one of the functions return `False`, the transition
will not happen. These functions should not have any side effects.
You can use ordinary functions
def can_publish(instance):
# No publishing after 17 hours
if datetime.datetime.now().hour > 17:
return False
return True
Or model methods
def can_destroy(self):
return self.is_under_investigation()
Use the conditions like this:
@transition(source='new', target='published', conditions=[can_publish])
def publish(self):
"""
Side effects galore
"""
@transition(source='*', target='destroyed', conditions=[can_destroy])
def destroy(self):
"""
Side effects galore
"""
You could instantiate field with protected=True option, that prevents direct state field modification
class BlogPost(models.Model):
state = FSMField(default='new', protected=True)
model = BlogPost()
model.state = 'invalid' # Raises AttributeError
### get_available_FIELD_transitions
You could specify FSMField explicitly in transition decorator.
class BlogPost(models.Model):
state = FSMField(default='new')
@transition(field=state, source='new', target='published')
def publish(self):
pass
This allows django_fsm to contribute to model class get_available_FIELD_transitions method,
that returns list of (target_state, method) available from current model state
### Foreign Key constraints support
If you store the states in the db table you could use FSMKeyField to
ensure Foreign Key database integrity.
### Signals
`django_fsm.signals.pre_transition` and `django_fsm.signals.post_transition` are called before
and after allowed transition. No signals on invalid transition are called.
Arguments sent with these signals:
**sender**
The model class.
**instance**
The actual instance being procceed
**name**
Transition name
**source**
Source model state
**target**
Target model state
### Drawing transitions
Renders a graphical overview of your models states transitions
# Create a dot file
$ ./manage.py graph_transitions -a > transitions.dot
# Create a PNG image file only for specific model
$ ./manage.py graph_transitions -o blog_transitions.png myapp.Blog
Changelog
---------
django 1.4.0 2011-12-21
* Add graph_transition command fro drawing state transition picture
django-fsm 1.3.0 2011-07-28
* Add direct field modification protection
django-fsm 1.2.0 2011-03-23
* Add pre_transition and post_transition signals
django-fsm 1.1.0 2011-02-22
* Add support for transition conditions
* Allow multiple FSMField in one model
* Contribute get_available_FIELD_transitions for model class
django-fsm 1.0.0 2010-10-12
* Initial public release
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