django model clean issue

Question

Im working in two models ralated via many to many, here's the relevant code:

class Curso(models.Model):
    horarios = models.ManyToManyField(Horario, related_name = 'cursos')
    ...
    def clean(self):
       ...
       self.horarios.all()
    def save(self,*args,**kwargs):
        self.full_clean()
        ...

Horarios has been already defined, now when i try to create an of curso in the admin interface i get an error pointing to self.horarios.all():

'Curso' instance needs to have a primary key value before a many-to-many relationship can be used.

And it makes sense as it has not been saved, so my problem is, how do i access the value of horarios in the current Curso instance that is being saved?.

thanks in advance

Wouldn't the Horario model have its own clean method? Why would you need to work with it in the Curso clean method? — jdi, May 16 '12 at 23:12
@jdi horario = schedule, i need horario not to be present on some Curso instance at the same time, that's how i validate them, iteraring over them. — loki, May 16 '12 at 23:38
Possible duplicate: http://stackoverflow.com/questions/6090859/django-instance-needs-to-have-a-primary-key-value-before-a-many-to-many-relatio — jdi, May 16 '12 at 23:39

score 2 · Answer 1 · answered May 17 '12 at 00:08

The error seems pretty straight forward to me -- you simply cannot call a ManyToMany before an object is saved.

You can reproduce the error: Curso().horarios

Clearly you can't be doing validation on relationships that can't possibly exist, so simply wrap your call in a if self.pk

if self.pk:
   self.horarios.all()

django model clean issue

1 Answers1