"""

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

class Place(models.Model):

    name = models.CharField(maxlength=50)

    address = models.CharField(maxlength=80)

    def __str__(self):

        return "%s the place" % self.name

class Restaurant(models.Model):

    place = models.OneToOneField(Place)

    serves_hot_dogs = models.BooleanField()

    serves_pizza = models.BooleanField()

    def __str__(self):

        return "%s the restaurant" % self.place.name

class Waiter(models.Model):

    restaurant = models.ForeignKey(Restaurant)

    name = models.CharField(maxlength=50)

    def __str__(self):

        return "%s the waiter at %s" % (self.name, self.restaurant)

class ManualPrimaryKey(models.Model):

    primary_key = models.CharField(maxlength=10, primary_key=True)

    name = models.CharField(maxlength = 50)

class RelatedModel(models.Model):

    link = models.OneToOneField(ManualPrimaryKey)

    name = models.CharField(maxlength = 50)

__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>

# Set the place back again, using assignment in the reverse direction

# Need to reget restaurant object first, because the reverse set

# can't update the existing restaurant instance

>>> p1.restaurant = r

>>> r.save()

>>> 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. This means there are multiple restaurants referencing

# a single place...

>>> 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()

"""}