Serializing a tree in Django

Question

is there any simple way to serialize a tree given by a model such as the Category shown below?

I'd like to get a json object like:

[ { 'name': 'cat1',
    'children': [ { 'name': 'cat11',
                    'children': [ ... ]
                ]
  }
  ...
]

Thanks

class Category(MPTTModel):
    name = models.CharField(max_length=50, unique=True)
    parent = models.ForeignKey('self', null=True, blank=True, related_name='children')
    order_key = models.IntegerField()

    class Meta:
        verbose_name_plural = 'Categories'

    class MPTTMeta:
        order_insertion_by = ['order_key']

    def __unicode__(self):
        return "%s" %(self.name)

Leopd · Accepted Answer · 2011-04-11T15:56:04.317

5

I think you'll have to walk the tree, and build an object which you serialize using JSON. I'm assuming your tree is acyclic, because otherwise it gets more complicated. I haven't tested this, but something like this will work (as long as you're sure you don't have cycles):

def serialize_to_json(self):
    return json.dumps(self.serializable_object())

def serializable_object(self):
    "Recurse into tree to build a serializable object"
    obj = {'name': self.name, 'children': []}
    for child in self.get_children():
        obj['children'].append(child.serializable_object())
    return obj

(Can't remember if children_set is the right way to get the list of children. Please comment if this is wrong.)

edited Apr 11 '11 at 15:56

answered Apr 08 '11 at 17:15

Leopd

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Thanks. Works with dump instead of dumps and get_children() instead of children_set.all(). – jul Apr 09 '11 at 09:16
Any reason not to turn that puppy into a list comprehension? – Mu Mind Sep 23 '12 at 21:32
1

Readability, that would be one long line of hard to read code ? – Jonas Geiregat Nov 21 '12 at 18:48
1

I see you are using `django-mptt`. Make sure you call `cache_tree_children()` before you evaluate your queryset. Otherwise it will hit the database every time you use `get_children()`. – dan-klasson Mar 08 '13 at 01:23

score 0 · Answer 2 · answered Apr 08 '11 at 17:07

0

Maybe Tasypie or Django-Piston can help? If not you can have a look at their source code to get some hints on how to do this.

answered Apr 08 '11 at 17:07

Pickels

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Serializing a tree in Django

2 Answers2

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