Hey Ludovic,

I simplified things a lot to illustrate my particular issue, but our 
permission system is actually pretty complex - the permissions can apply to 
any individual object, and they are also hierarchical like those that would 
apply to a folder system. I found there were decent extensions to the 
Django permission system to handle object-level permissions, and 
hierarchical permissions, but not both.

On Wednesday, September 21, 2016 at 9:11:44 AM UTC-6, ludovic coues wrote:
>
> Unrelated, do you have any reason to not reuse the existing django 
> permission system ? 
>
> 2016-09-21 16:41 GMT+02:00 TheBeardedTemplar <thebeard...@gmail.com 
> <javascript:>>: 
> > Hey all, 
> > 
> > I'm just getting started with GenericForeignKeys and I've run into a 
> small 
> > point of confusion. I'm implementing a very general permission system as 
> > follows: 
> > 
> > class Permission(models.Model): 
> >     """ 
> >     This stores permissions for a single object. 
> >     """ 
> >     #These 3 fields are used to implement a generic foreign key 
> >     content_type = models.ForeignKey(ContentType) 
> >     object_id = models.PositiveIntegerField() 
> >     model = GenericForeignKey() 
> > 
> >     user = models.ForeignKey(User) 
> > 
> >     #Permissions 
> >     read = models.BooleanField(default=False) 
> >     write = models.BooleanField(default=False) 
> >     delete = models.BooleanField(default=False) 
> > 
> > 
> > 
> > I also have a check permission function as follows: 
> >     def checkPermission(self, obj, user, action): 
> >         try: 
> >             p = Permission.objects.get(model=obj, user=user) 
> >             return getattr(p, action) 
> >         except ObjectPermission.DoesNotExist: 
> >             return False 
> > 
> > Currently this fails because I'm trying to access the GenericForeignKey 
> > directly, and I get this error: 
> > django.core.exceptions.FieldError: Field 'model' does not generate an 
> > automatic reverse relation and therefore cannot be used for reverse 
> > querying. If it is a GenericForeignKey, consider adding a 
> GenericRelation. 
> > 
> > I've spent a while reading about GenericRelations but I'm still not 
> exactly 
> > sure how to go about this. The Django documentation shows using 
> > GenericRelation fields on the models that my Permission points to, but 
> it 
> > can point to many many different things and I'm hoping to get a way to 
> use 
> > this functionality without putting a GenericRelation on every possible 
> > linked to model. 
> > 
> > Thanks! 
> > 
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> > 
> https://groups.google.com/d/msgid/django-users/9160074b-4b1c-490b-93d9-d607895ba4eb%40googlegroups.com.
>  
>
> > For more options, visit https://groups.google.com/d/optout. 
>
>
>
> -- 
>
> Cordialement, Coues Ludovic 
> +336 148 743 42 
>

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