Question

I have a WorderOrder class that has predefined work order types:

class WorkOrder( models.Model ) :
    WORK_TYPE_CHOICES = (
        ( 'hc', 'Heating and cooling' ),
        ( 'el', 'Electrical'          ),
        ( 'pl', 'Plumbing'            ),
        ( 'ap', 'Appliances'          ),
        ( 'pe', 'Pests'               ),
        ( 'ex', 'Exterior'            ),
        ( 'in', 'Interior'            ),
        ( 'ot', 'Others'              ),
    )

    work_type = models.CharField( max_length = 2, choices = WORK_TYPE_CHOICES )
    vendor    = models.ForeignKey( Vendor, null = True, blank = True )

Therefore each order must have one work order type. Later down the road, a vendor can also be assigned to a work order.

I want the Vendor class to have a M2M relationship to the same work order choices in the WorkOrder class. In other words, each vendor are able to do one or many work types. For example, Bob’s Plumbing can only do “Plumbing”, whereas Solid Home Repair can do “Electrical”, “Plumbing”, “Exterior”, and “Interior”.

I understand I can create another table called WorkType and use foreign keys from WorkOrder and a M2M from Vendor, but since I feel I won’t be changing the work type choices, I would rather have them predefined in models.py.

Also if I can predefine it in models.py, then I don’t have to pre-populate the table WorkType during deployments and upgrades.

Answer 1

Some options for you:

1. create a model for work_type_choices, instantiate the records (hc, el, etc), then use a manytomany field, or

2. create a charfield and save CSV values to it (eg: “hc, el”), spliting/joining the value into it’s elements as required, or

3. encapsule the above charfield and functions into a custom field and use that

4. leverage someone else’s snippet, eg:
   http://djangosnippets.org/snippets/1200/