Question

Let’s say I have a set of Django Models:

class Article(models.Model):
    title = models.CharField(max_length=100, default='')
    content = models.TextField(default='', blank=False)
    created_at = models.DateTimeField(auto_now=True)
    creator = models.ForeignKey(User, null=True, blank=True)
    score = models.ForeignKey('Score', blank=True, null=True)
    points = models.ManyToManyField('Points')


class Score(models.Model):
    value = models.IntegerField()
    created_at = models.DateTimeField(auto_now_add=True)
    creator = models.ForeignKey(User, null=True, blank=True)


class Points(models.Model):
    value = models.DecimalField(max_digits=3, decimal_places=1)
    caption = models.CharField(max_length=20, default='')
    created_at = models.DateTimeField(auto_now_add=True)
    creator = models.ForeignKey(User, blank=True, null=True)

And now I somehow get an instance of a Score model (without actually knowing that this is Score model) and an instance of Points model (again, without knowing that this is Points model):

>>> type(s)
<class 'myapp.models.Score'>
>>> type(p)
<class 'myapp.models.Points'>

Now I can get access to a set of related Article instances via the following code:

>>> s.article_set
<django.db.models.fields.related.RelatedManager object at 0x10d1e8610>
>>> p.article_set
<django.db.models.fields.related.ManyRelatedManager object at 0x10d1e8850>

But this is the case where I know actual DB schema and I know that attributes are called article_set. In my case I do not know the actual DB scema. And I want to get all the RelatedManager attributes of the current model instance.

I think that it is possible to implement this via ._meta attribute but I didn’t manage to do that while trying. So I would probably need an actual working example of something like get_related_managers(self) method implementation.

Answer 1

This seems to work for me:

def get_related_managers(self):
    managers = []
    for related_object in self._meta.get_all_related_objects():
        managers.append(getattr(self, related_object.get_accessor_name()))
    return managers

You will also have to loop through self._meta.get_all_related_many_to_many_objects() if you want many to manys as well.

UPD: In newer django versions, _meta does not have such methods, but the same can be done with self._meta.related_objects and self._meta.many_to_many.