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"""
10. One-to-one relationships
To define a one-to-one relationship, use ``OneToOneField()``.
In this example, a ``Place`` optionally can be a ``Restaurant``.
"""
from django.db import models, transaction, IntegrityError
class Place(models.Model):
name = models.CharField(max_length=50)
address = models.CharField(max_length=80)
def __unicode__(self):
return u"%s the place" % self.name
class Restaurant(models.Model):
place = models.OneToOneField(Place, primary_key=True)
serves_hot_dogs = models.BooleanField()
serves_pizza = models.BooleanField()
def __unicode__(self):
return u"%s the restaurant" % self.place.name
class Waiter(models.Model):
restaurant = models.ForeignKey(Restaurant)
name = models.CharField(max_length=50)
def __unicode__(self):
return u"%s the waiter at %s" % (self.name, self.restaurant)
class ManualPrimaryKey(models.Model):
primary_key = models.CharField(max_length=10, primary_key=True)
name = models.CharField(max_length = 50)
class RelatedModel(models.Model):
link = models.OneToOneField(ManualPrimaryKey)
name = models.CharField(max_length = 50)
class MultiModel(models.Model):
link1 = models.OneToOneField(Place)
link2 = models.OneToOneField(ManualPrimaryKey)
name = models.CharField(max_length=50)
def __unicode__(self):
return u"Multimodel %s" % self.name
__test__ = {'API_TESTS':"""
# Create a couple of Places.
>>> p1 = Place(name='Demon Dogs', address='944 W. Fullerton')
>>> p1.save()
>>> p2 = Place(name='Ace Hardware', address='1013 N. Ashland')
>>> p2.save()
# Create a Restaurant. Pass the ID of the "parent" object as this object's ID.
>>> r = Restaurant(place=p1, serves_hot_dogs=True, serves_pizza=False)
>>> r.save()
# A Restaurant can access its place.
>>> r.place
<Place: Demon Dogs the place>
# A Place can access its restaurant, if available.
>>> p1.restaurant
<Restaurant: Demon Dogs the restaurant>
# p2 doesn't have an associated restaurant.
>>> p2.restaurant
Traceback (most recent call last):
...
DoesNotExist: Restaurant matching query does not exist.
# Set the place using assignment notation. Because place is the primary key on
# Restaurant, the save will create a new restaurant
>>> r.place = p2
>>> r.save()
>>> p2.restaurant
<Restaurant: Ace Hardware the restaurant>
>>> r.place
<Place: Ace Hardware the place>
>>> p2.id
2
# Set the place back again, using assignment in the reverse direction.
>>> p1.restaurant = r
>>> p1.restaurant
<Restaurant: Demon Dogs the restaurant>
>>> r = Restaurant.objects.get(pk=1)
>>> r.place
<Place: Demon Dogs the place>
# Restaurant.objects.all() just returns the Restaurants, not the Places.
# Note that there are two restaurants - Ace Hardware the Restaurant was created
# in the call to r.place = p2.
>>> Restaurant.objects.all()
[<Restaurant: Demon Dogs the restaurant>, <Restaurant: Ace Hardware the restaurant>]
# Place.objects.all() returns all Places, regardless of whether they have
# Restaurants.
>>> Place.objects.order_by('name')
[<Place: Ace Hardware the place>, <Place: Demon Dogs the place>]
>>> Restaurant.objects.get(place__id__exact=1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(pk=1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(place__exact=1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(place__exact=p1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(place=1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(place=p1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(place__pk=1)
<Restaurant: Demon Dogs the restaurant>
>>> Restaurant.objects.get(place__name__startswith="Demon")
<Restaurant: Demon Dogs the restaurant>
>>> Place.objects.get(id__exact=1)
<Place: Demon Dogs the place>
>>> Place.objects.get(pk=1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant__place__exact=1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant__place__exact=p1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant__pk=1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant=1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant=r)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant__exact=1)
<Place: Demon Dogs the place>
>>> Place.objects.get(restaurant__exact=r)
<Place: Demon Dogs the place>
# Add a Waiter to the Restaurant.
>>> w = r.waiter_set.create(name='Joe')
>>> w.save()
>>> w
<Waiter: Joe the waiter at Demon Dogs the restaurant>
# Query the waiters
>>> Waiter.objects.filter(restaurant__place__pk=1)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
>>> Waiter.objects.filter(restaurant__place__exact=1)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
>>> Waiter.objects.filter(restaurant__place__exact=p1)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
>>> Waiter.objects.filter(restaurant__pk=1)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
>>> Waiter.objects.filter(id__exact=1)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
>>> Waiter.objects.filter(pk=1)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
>>> Waiter.objects.filter(restaurant=1)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
>>> Waiter.objects.filter(restaurant=r)
[<Waiter: Joe the waiter at Demon Dogs the restaurant>]
# Delete the restaurant; the waiter should also be removed
>>> r = Restaurant.objects.get(pk=1)
>>> r.delete()
# One-to-one fields still work if you create your own primary key
>>> o1 = ManualPrimaryKey(primary_key="abc123", name="primary")
>>> o1.save()
>>> o2 = RelatedModel(link=o1, name="secondary")
>>> o2.save()
# You can have multiple one-to-one fields on a model, too.
>>> x1 = MultiModel(link1=p1, link2=o1, name="x1")
>>> x1.save()
>>> o1.multimodel
<MultiModel: Multimodel x1>
# This will fail because each one-to-one field must be unique (and link2=o1 was
# used for x1, above).
>>> sid = transaction.savepoint()
>>> try:
... MultiModel(link1=p2, link2=o1, name="x1").save()
... except Exception, e:
... if isinstance(e, IntegrityError):
... print "Pass"
... else:
... print "Fail with %s" % type(e)
Pass
>>> transaction.savepoint_rollback(sid)
"""}
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