writing-models.rst

Writing Models

Models look similar to typical Django models. A neo4django model definition might look like this:

from neo4django.db import models

class Person(models.NodeModel):
    name = models.StringProperty()
    age = models.IntegerProperty()

    friends = models.Relationship('self',rel_type='friends_with')

Properties

As you can see, some basic properties are provided:

class OnlinePerson(Person):
    email = models.EmailProperty()
    homepage = models.URLProperty()

Some property types can also be indexed by neo4django. This will speed up subsequent queries based on those properties:

class EmployedPerson(Person):
    job_title = models.StringProperty(indexed=True)

All instances of EmployedPerson will have their job_title properties indexed.

For a list of included property types, check out :mod:`neo4django.db.models.__init__`.

Relationships

Relationships are simple. Instead of :class:`~django.db.models.ForeignKey`, :class:`~django.db.models.ManyToManyField`, or :class:`~django.db.models.OneToOneField`, just use :class:`~neo4django.db.models.Relationship`. In addition to the relationship target, you can specify a relationship type and direction, cardinality, and the name of the relationship on the target model:

class Pet(models.NodeModel):
    owner = models.Relationship(Person,
                                rel_type='owns',
                                single=True,
                                related_name='pets'
                               )

Note that specifying cardinality with single or related_single is optional- Neo4j doesn't enforce any relational cardinality. Instead, these options are provided as a modeling convenience.

You can also target a model that has yet to be defined with a string:

class Pet(models.NodeModel):
    owner = models.Relationship('Person',
                                rel_type='owns',
                                single=True,
                                related_name='pets'
                               )

And then in the interpreter:

>>> pete = Person.objects.create(name='Pete', age=30)
>>> garfield = Pet.objects.create()
>>> pete.pets.add(garfield)
>>> pete.save()
>>> list(pete.pets.all())
[<Pet: Pet object>]

If you care about the order of a relationship, add the preserve_ordering=True option. Related objects will be retrieved in the order they were saved.

Got a few models written? To learn about retrieving data, see :doc:`querying`.