django-river 0.3.3

Django Workflow Library

River is a open source workflow system for Django which support on the fly changes on every item in workflow instead of hardcoding states and transitions.

Main goal of developing this framework is to be able to edit any workflow item on the fly. This means, all elements in workflow like states, transitions, user authorizations(permission), group authorization are editable. To do this, all data about the workflow item is persisted into DB. Hence, they can be changed without touching the code and re-deploying your application.

There is ordering aprovments for a transition functionality in django-river. It also provides skipping specific transition of a specific objects.

Documentation

Online documentation is available at http://django-river.rtfd.org/.

Installation

• Install it

  pip install django-river

• Configure settings

  INSTALLED_APPS=[
  ...
  river
  ...
  ]

• Migrate your application

  python manage.py migrate

• In your model class which will be processing in workflow;

from django.db import models
from river.models.fields.state import StateField

class MyModel(models.Model):
    my_state_field = StateField()

That’s it. Whenever your new model object is saved, it’s state field will be initialized according to given meta data about workflow. To know how to do your workflow confirmation(states, transitions, permissions etc.), see the next part.

Usage for End User

1. Define your states.

2. Define your state transitions.

3. Define your approvement meta which contains permissions and groups authorization for transitions. Approvement order is also given here.

We are now ready to workflowing :)

Whenever an object of MyModel is inserted in your system, all its workflow initialization is done by django-river.

Usage for Developer

Signals:

pre_transition: it is fired before any transition occured.

Args	Description
workflow_object	Your object on transition
field	Field which you registered object for
source_state	Transition source state object
destination_state	Transition destination state object
appovement	Approvement object

post_transition: it is fired before any transition occured.

Args	Description
workflow_object	Your object on transition
field	Field which you registered object for
source_state	Transition source state object
destination_state	Transition destination state object
appovement	Approvement object

pre_approved: it is fired before any approvement occured. Transition does not have to be occured.

Args	Description
workflow_object	Your object approved
field	Field which you registered object for
appovement	Approvement object
track	Approvement track object

post_approved: it is fired before any approvement occured. Transition does not have to be occured.

Args	Description
workflow_object	Your object approved
field	Field which you registered object for
appovement	Approvement object
track	Approvement track object

pre_final: it is fired before any workflow is completed.

Args	Description
workflow_object	Your object on final
field	Field which you registered object for

post_final: it is fired before any workflow is completed.

Args	Description
workflow_object	Your object on final
field	Field which you registered object for

Handlers:

Handlers are different from django-river signals. These are for spesific object, spesific source_state, spesific destination_state etc. It is fired when the condition is matched.

PreCompletedHandler:

Before an object is on final state, if the condition is match; means object is suitable, it is fired;

from river.handlers.completed import PreCompletedHandler

def handler(my_object,field,*args,**kwargs):
    do_something_with(object,field)

PreCompletedHandler.register(handler,my_object,'my_state_field')

register method parameter

Args	Description
workflow_object	Your object	Required
field	Field which you registered object for	Required

PostCompletedHandler:

After an object is on final state, if the condition is match; means object is suitable, it is fired;

from river.handlers.completed import PostCompletedHandler

def handler(my_object,field,*args,**kwargs):
    do_something_with(object,field)

PostCompletedHandler.register(handler,my_object,'my_state_field')

register method parameter

Args	Description
workflow_object	Your object	Required
field	Field which you registered object for	Required

PreTransitionHandler:

Before any transition occurred, if the condition is match; means object, source_state,destination state are suitable, it is fired;

from river.handlers.transition import PreTransitionHandler

def handler(my_object,field,*args,**kwargs):
    do_something_with(object,field)

PreTransitionHandler.register(handler,my_object,'my_state_field')

register method parameter

Args	Description
workflow_object	Your object	Required
field	Field which you registered object for	Required
source_state	Source state of the tranition	Optional
desination_satte	Destinatio state of the tranition	Optional

PostTransitionHandler:

After any transition occurred, if the condition is match; means object, source_state,destination state are suitable, it is fired;

from river.handlers.transition import PostTransitionHandler

def handler(my_object,field,*args,**kwargs):
    do_something_with(object,field)

PostTransitionHandler.register(handler,my_object,'my_state_field')

register method parameter

Args	Description
workflow_object	Your object	Required
field	Field which you registered object for	Required
source_state	Source state of the tranition	Optional
desination_satte	Destinatio state of the tranition	Optional

Models:

States:

Indicates states in your state machine.

Transitions:

These are transition between your states. There must be only one initial state which is in a transition as destination state but no source state to make django-river find it on object creation.

Approvement Meta:

These are approvement meta of transitions that describes which user permission or user group will be allowed to approve the transition. These are kind of template for approvements will be created for each object. An order can also be given here for the transition. This means, If you want to order approvement for a transition, you can define it. Assume s1 and s2 are our states and there is a transition defined between them and we have two approvement meta on this transition. They shall be forpermission1 and permission2. If you want object is on approval first permission1 and after it is approved by permission1, then it is on approval the second permission which is permission2, you can do it with djang-river by defining order in this model.

Approvement:

There are state machines paths which is needed to be approved for every particular object. Approvements are generated on your model object creation by using approvement meta. This is whole path for the created object. Do not add or edit this model data unless you don’t need specific objects editing like skiping, overriding permissions and groups.