处理自引用外键； 模特妈妈

Question

I am getting the typical runtime error of self referencing FKs testing django with fake objects:

... last 4 frames repeated, from the frame below ...

/home/cchilders/.virtualenvs/clientsite/lib/python3.4/site-packages/model_mommy/mommy.py in make(model, _quantity, make_m2m, **attrs)
     96         return [mommy.make(**attrs) for i in range(_quantity)]
     97     else:
---> 98         return mommy.make(**attrs)
     99 
    100 

RuntimeError: maximum recursion depth exceeded while calling a Python object

the model:

class ItemGroup(models.Model):
    parent = models.ForeignKey('self', db_column='parent_id')
    name = models.CharField(max_length=255)
    value = models.CharField(max_length=255, unique=True)

    class Meta:
        db_table = u'item_groups'

    def __str__(self):
        return self.value

    def __repr__(self):
        return '<{} {}: {}>'.format(self.__class__.__name__, self.pk, self.value)

The docs are sparse on referencing yourself as FK. How can you fake an instance that requires on one of itself with modelmommy? Thank you

Answer 1

First of all, I think you should make the parent field nullable; parent = models.ForeignKey('self', db_column='parent_id', null=True, blank=True) that means you will have a base object from which to start referencing.

With model mommy, you can first create a fake parent, then assign the parent to the child.

parent_item_group = mommy.make(ItemGroup)
child_item_group = mommy.make(ItemGroup, parent=parent_item_group)