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Tutorial
========
Create a basic model for your tree. In this example we'll use a Materialized Path tree:
.. code-block:: python
from django.db import models
from django.utils.encoding import python_2_unicode_compatible
from treebeard.mp_tree import MP_Node
@python_2_unicode_compatible
class Category(MP_Node):
name = models.CharField(max_length=30)
node_order_by = ['name']
def __str__(self):
return 'Category: {}'.format(self.name)
This example works on Python 3 as well as on Python 2. If you don't need Python 2 support
remove the ``@python_2_unicode_compatible`` decorator.
Run syncdb:
.. code-block:: console
$ python manage.py syncdb
Let's create some nodes:
.. code-block:: python
>>> from treebeard_tutorial.models import Category
>>> get = lambda node_id: Category.objects.get(pk=node_id)
>>> root = Category.add_root(name='Computer Hardware')
>>> node = get(root.pk).add_child(name='Memory')
>>> get(node.pk).add_sibling(name='Hard Drives')
<Category: Category: Hard Drives>
>>> get(node.pk).add_sibling(name='SSD')
<Category: Category: SSD>
>>> get(node.pk).add_child(name='Desktop Memory')
<Category: Category: Desktop Memory>
>>> get(node.pk).add_child(name='Laptop Memory')
<Category: Category: Laptop Memory>
>>> get(node.pk).add_child(name='Server Memory')
<Category: Category: Server Memory>
.. note::
Why retrieving every node again after the first operation? Because
``django-treebeard`` uses raw queries for most write operations,
and raw queries don't update the django objects of the db entries they
modify. See: :doc:`caveats`.
We just created this tree:
.. digraph:: introduction_digraph
"Computer Hardware";
"Computer Hardware" -> "Hard Drives";
"Computer Hardware" -> "Memory";
"Memory" -> "Desktop Memory";
"Memory" -> "Laptop Memory";
"Memory" -> "Server Memory";
"Computer Hardware" -> "SSD";
You can see the tree structure with code:
.. code-block:: python
>>> Category.dump_bulk()
[{'id': 1, 'data': {'name': u'Computer Hardware'},
'children': [
{'id': 3, 'data': {'name': u'Hard Drives'}},
{'id': 2, 'data': {'name': u'Memory'},
'children': [
{'id': 5, 'data': {'name': u'Desktop Memory'}},
{'id': 6, 'data': {'name': u'Laptop Memory'}},
{'id': 7, 'data': {'name': u'Server Memory'}}]},
{'id': 4, 'data': {'name': u'SSD'}}]}]
>>> Category.get_annotated_list()
[(<Category: Category: Computer Hardware>,
{'close': [], 'level': 0, 'open': True}),
(<Category: Category: Hard Drives>,
{'close': [], 'level': 1, 'open': True}),
(<Category: Category: Memory>,
{'close': [], 'level': 1, 'open': False}),
(<Category: Category: Desktop Memory>,
{'close': [], 'level': 2, 'open': True}),
(<Category: Category: Laptop Memory>,
{'close': [], 'level': 2, 'open': False}),
(<Category: Category: Server Memory>,
{'close': [0], 'level': 2, 'open': False}),
(<Category: Category: SSD>,
{'close': [0, 1], 'level': 1, 'open': False})]
Read the :class:`treebeard.models.Node` API reference for detailed info.
.. _`treebeard mercurial repository`:
http://code.tabo.pe/django-treebeard
.. _`latest treebeard version from PyPi`:
http://pypi.python.org/pypi/django-treebeard/
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