Question

Currently I have three models in Django that create a circular reference:

A User can live in a Location.
A Location must be part of a Property.
A Property must have an owner, which is a User.

The reason I want each User to specify a location is for people living in apartments. An apartment tenant would live in a numbered room, but a house tenant wouldn’t. But notice that location can also simply be just a property (ie a house tenant lives in a location which is just the property with an address; the property doesn’t have room numbers, floors, or buildings.).

Here is the (stripped down) code:

class User( models.Model ) :
    TYPE_CHOICES = (
        ( 't', 'tenant'           ),
        ( 'o', 'property owner'   ),
        ( 'v', 'vendor'           ),
        ( 'm', 'property manager' ),
    )

    user_type  = models.CharField( max_length = 1, choices = TYPE_CHOICES, default = 't' )
    first_name = models.CharField( max_length = 135 )
    last_name  = models.CharField( max_length = 135 )
    location   = models.ForeignKey( Location, null = True, blank = True )

class Property( models.Model ) :
    name             = models.CharField( max_length = 135 )
    owner            = models.ForeignKey( User )
    address_line_one = models.CharField( max_length = 135 )
    address_line_two = models.CharField( max_length = 135, blank = True )
    city             = models.CharField( max_length = 135 )
    state            = models.CharField( max_length = 135 )
    zip_code         = models.CharField( max_length = 135 )

class Location( models.Model ) :
    room       = models.CharField( max_length = 135, blank = True )
    floor      = models.CharField( max_length = 135, blank = True )
    building   = models.CharField( max_length = 135, blank = True )
    prop       = models.ForeignKey( Property )

Please let me know if you guys need more clarification or code. Thanks in advance!

Answer 1

Like the docs say, you can use a string to specify the app and model to use in a relation.

If you need to create a relationship on a model that has not yet been defined, you can use the name of the model, rather than the model object itself