Define workflow

Often records follow a workflow to change their state. For example the opportunity can be converted or lost. Tryton has a Workflow class that provides the tooling to follow a workflow based on the field defined in _transition_state which is by default state.

First we need to inherit from Workflow and add a Selection field to store the state of the record:

from trytond.model import Workflow
...
class Opportunity(Workflow, ModelSQL, ModelView):
   ...
   state = fields.Selection([
             ('draft', "Draft"),
             ('converted', "Converted"),
             ('lost', "Lost"),
             ], "State",
       required=True, readonly=True, sort=False)

   @classmethod
   def default_state(cls):
       return 'draft'

We must define the allowed transitions between states by filling the _transitions set with tuples using the __setup__() method:

class Opportunity(Workflow, ModelSQL, ModelView):
   ...
   @classmethod
   def __setup__(cls):
      super().__setup__()
      cls._transitions.update({
                ('draft', 'converted'),
                ('draft', 'lost'),
                })

For each target state, we must define a transition() method. For example when the opportunity is converted we fill the end_date field with today:

class Opportunity(Workflow, ModelSQL, ModelView):
   ...
   @classmethod
   @Workflow.transition('converted')
   def convert(cls, opportunities):
       pool = Pool()
       Date = pool.get('ir.date')
       cls.write(opportunities, {
           'end_date': Date.today(),
           })

Note

We let you define the transition method for lost.

Now we need to add a button for each transition so the user can trigger them.

We must declare the button in the _buttons dictionary and decorate the transition method with the button() to be callable from the client:

class Opportunity(Workflow, ModelSQL, ModelView):
    ...
    @classmethod
    def __setup__(cls):
        ...
        cls._buttons.update({
                'convert': {},
                'lost': {},
                })

    @classmethod
    @ModelView.button
    @Workflow.transition('converted')
    def convert(cls, opportunities):
        ...

    @classmethod
    @ModelView.button
    @Workflow.transition('lost')
    def lost(cls, opportunities):
        ...

Every button must also be recorded as a Model Button to define its label (and also the access right). We must add to the opportunity.xml file:

<tryton>
   <data>
      ...
      <record model="ir.model.button" id="opportunity_convert_button">
         <field name="model">training.opportunity</field>
         <field name="name">convert</field>
         <field name="string">Convert</field>
      </record>

      <record model="ir.model.button" id="opportunity_lost_button">
         <field name="model">training.opportunity</field>
         <field name="name">lost</field>
         <field name="string">Lost</field>
      </record>
   </data>
</tryton>

Now we can add the state field and the buttons in the form view. The buttons can be grouped under a group tag. This is how the view/opportunity_form.xml must be adapted:

<form>
   ...
   <label name="state"/>
   <field name="state"/>
   <group col="2" colspan="2" id="button">
      <button name="lost" icon="tryton-cancel"/>
      <button name="convert" icon="tryton-forward"/>
   </group>
</form>

Note

We let you add the state field on the list view.

Update database

As we have defined new fields and XML records, we need to update the database with:

$ trytond-admin -d test --all

And restart the server and reconnect with the client to test the workflow:

$ trytond

Exercise

As exercise we let you add a transition between lost and draft which will clear the end_date.

Let’s continue with adding more reaction with dynamic state.