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1 """ |
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2 23. Giving models a custom manager |
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3 |
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4 You can use a custom ``Manager`` in a particular model by extending the base |
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5 ``Manager`` class and instantiating your custom ``Manager`` in your model. |
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6 |
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7 There are two reasons you might want to customize a ``Manager``: to add extra |
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8 ``Manager`` methods, and/or to modify the initial ``QuerySet`` the ``Manager`` |
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9 returns. |
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10 """ |
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11 |
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12 from django.db import models |
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13 |
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14 # An example of a custom manager called "objects". |
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15 |
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16 class PersonManager(models.Manager): |
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17 def get_fun_people(self): |
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18 return self.filter(fun=True) |
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19 |
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20 class Person(models.Model): |
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21 first_name = models.CharField(max_length=30) |
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22 last_name = models.CharField(max_length=30) |
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23 fun = models.BooleanField() |
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24 objects = PersonManager() |
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25 |
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26 def __unicode__(self): |
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27 return u"%s %s" % (self.first_name, self.last_name) |
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28 |
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29 # An example of a custom manager that sets get_query_set(). |
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30 |
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31 class PublishedBookManager(models.Manager): |
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32 def get_query_set(self): |
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33 return super(PublishedBookManager, self).get_query_set().filter(is_published=True) |
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34 |
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35 class Book(models.Model): |
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36 title = models.CharField(max_length=50) |
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37 author = models.CharField(max_length=30) |
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38 is_published = models.BooleanField() |
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39 published_objects = PublishedBookManager() |
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40 authors = models.ManyToManyField(Person, related_name='books') |
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41 |
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42 def __unicode__(self): |
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43 return self.title |
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44 |
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45 # An example of providing multiple custom managers. |
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46 |
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47 class FastCarManager(models.Manager): |
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48 def get_query_set(self): |
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49 return super(FastCarManager, self).get_query_set().filter(top_speed__gt=150) |
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50 |
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51 class Car(models.Model): |
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52 name = models.CharField(max_length=10) |
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53 mileage = models.IntegerField() |
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54 top_speed = models.IntegerField(help_text="In miles per hour.") |
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55 cars = models.Manager() |
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56 fast_cars = FastCarManager() |
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57 |
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58 def __unicode__(self): |
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59 return self.name |