python - Django: GenericForeignKey and unique_together -

in application i'm working on i'm trying share access tokens within company. example: local office can use headquarter's tokens post on facebook page.

class accesstoken(models.model):     """abstract class access tokens."""     owner = models.foreignkey('publish.publisher')     socialmediachannel = models.integerfield(         choices=socialmediachannellist, null=false, blank=false     )     lastupdate = models.datefield(auto_now=true)      class meta:         abstract = true 

since facebook, twitter , other social media sites handle access tokens in own way made , abstract class accesstoken. each site gets own class e.g.

class facebookaccesstoken(accesstoken):     # class stuff 

after doing reading found out must use genericforeignkey point classes inherit accesstoken. made following class:

class shareaccesstoken(models.model):     """share access tokens other publishers."""     sharedwith = models.foreignkey('publish.publisher')     sharedby = models.foreignkey(user)      # foreignkey abstract model's children     contenttype = models.foreignkey(contenttype)     objectid = models.positiveintegerfield()     contentobject = genericforeignkey('contenttype', 'objectid')      class meta:         unique_together = (('contentobject', 'sharedwith')) 

when run django test server following error:

core.shareaccesstoken: (models.e016) 'unique_together' refers field 'contentobject' not local model 'shareaccesstoken'. hint: issue may caused multi-table inheritance.

i don't understand why error, first time using genericforeignkey. doing wrong?

if there smarter way share access tokens love hear it.

your use of generic foreign key in situation correct.

the error coming unique_together declaration in model. unique_together can used columns exist in database. since contentobject not real column, django complains constraint.

instead, can following:

unique_together = (('contenttype', 'contentid', 'sharedwidth'),) 

this equivalent had defined in question because contentobject combination of contenttype , contentid behind scenes.