107 lines
3.1 KiB
Python
107 lines
3.1 KiB
Python
"""
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10. One-to-one relationships
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To define a one-to-one relationship, use ``OneToOneField()``.
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In this example, a ``Place`` optionally can be a ``Restaurant``.
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"""
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from django.db import models
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class Place(models.Model):
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name = models.CharField(maxlength=50)
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address = models.CharField(maxlength=80)
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def __repr__(self):
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return "%s the place" % self.name
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class Restaurant(models.Model):
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place = models.OneToOneField(Place)
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serves_hot_dogs = models.BooleanField()
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serves_pizza = models.BooleanField()
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def __repr__(self):
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return "%s the restaurant" % self.get_place().name
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class Waiter(models.Model):
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restaurant = models.ForeignKey(Restaurant)
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name = models.CharField(maxlength=50)
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def __repr__(self):
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return "%s the waiter at %r" % (self.name, self.get_restaurant())
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API_TESTS = """
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# Create a couple of Places.
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>>> p1 = Place(name='Demon Dogs', address='944 W. Fullerton')
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>>> p1.save()
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>>> p2 = Place(name='Ace Hardware', address='1013 N. Ashland')
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>>> p2.save()
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# Create a Restaurant. Pass the ID of the "parent" object as this object's ID.
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>>> r = Restaurant(place=p1, serves_hot_dogs=True, serves_pizza=False)
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>>> r.save()
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# A Restaurant can access its place.
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>>> r.get_place()
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Demon Dogs the place
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# A Place can access its restaurant, if available.
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>>> p1.get_restaurant()
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Demon Dogs the restaurant
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# p2 doesn't have an associated restaurant.
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>>> p2.get_restaurant()
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Traceback (most recent call last):
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...
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DoesNotExist: Restaurant does not exist for {'place__id__exact': ...}
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# Restaurant.objects.get_list() just returns the Restaurants, not the Places.
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>>> Restaurant.objects.get_list()
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[Demon Dogs the restaurant]
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# Place.objects.get_list() returns all Places, regardless of whether they have
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# Restaurants.
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>>> Place.objects.get_list(order_by=['name'])
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[Ace Hardware the place, Demon Dogs the place]
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>>> Restaurant.objects.get_object(place__id__exact=1)
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Demon Dogs the restaurant
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>>> Restaurant.objects.get_object(pk=1)
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Demon Dogs the restaurant
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>>> Restaurant.objects.get_object(place__exact=1)
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Demon Dogs the restaurant
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>>> Restaurant.objects.get_object(place__pk=1)
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Demon Dogs the restaurant
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>>> Restaurant.objects.get_object(place__name__startswith="Demon")
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Demon Dogs the restaurant
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>>> Place.objects.get_object(id__exact=1)
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Demon Dogs the place
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>>> Place.objects.get_object(pk=1)
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Demon Dogs the place
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>>> Place.objects.get_object(restaurants__place__exact=1)
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Demon Dogs the place
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>>> Place.objects.get_object(restaurants__pk=1)
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Demon Dogs the place
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# Add a Waiter to the Restaurant.
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>>> w = r.add_waiter(name='Joe')
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>>> w.save()
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>>> w
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Joe the waiter at Demon Dogs the restaurant
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# Query the waiters
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>>> Waiter.objects.get_list(restaurant__place__exact=1)
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[Joe the waiter at Demon Dogs the restaurant]
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>>> Waiter.objects.get_list(restaurant__pk=1)
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[Joe the waiter at Demon Dogs the restaurant]
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>>> Waiter.objects.get_list(id__exact=1)
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[Joe the waiter at Demon Dogs the restaurant]
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>>> Waiter.objects.get_list(pk=1)
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[Joe the waiter at Demon Dogs the restaurant]
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# Delete the restaurant; the waiter should also be removed
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>>> r = Restaurant.objects.get_object(pk=1)
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>>> r.delete()
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"""
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