author | Daniel Diniz <ajaksu@gmail.com> |
Fri, 03 Jul 2009 12:10:24 +0200 | |
changeset 2500 | ecc16ffe174b |
parent 109 | 620f9b141567 |
permissions | -rwxr-xr-x |
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""" |
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8. get_latest_by |
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Models can have a ``get_latest_by`` attribute, which should be set to the name |
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of a DateField or DateTimeField. If ``get_latest_by`` exists, the model's |
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manager will get a ``latest()`` method, which will return the latest object in |
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the database according to that field. "Latest" means "having the date farthest |
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into the future." |
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""" |
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|
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from django.db import models |
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class Article(models.Model): |
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headline = models.CharField(maxlength=100) |
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pub_date = models.DateField() |
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expire_date = models.DateField() |
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class Meta: |
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get_latest_by = 'pub_date' |
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|
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def __str__(self): |
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return self.headline |
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|
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class Person(models.Model): |
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name = models.CharField(maxlength=30) |
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birthday = models.DateField() |
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# Note that this model doesn't have "get_latest_by" set. |
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def __str__(self): |
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return self.name |
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__test__ = {'API_TESTS':""" |
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# Because no Articles exist yet, latest() raises ArticleDoesNotExist. |
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>>> Article.objects.latest() |
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Traceback (most recent call last): |
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... |
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DoesNotExist: Article matching query does not exist. |
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# Create a couple of Articles. |
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>>> from datetime import datetime |
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>>> a1 = Article(headline='Article 1', pub_date=datetime(2005, 7, 26), expire_date=datetime(2005, 9, 1)) |
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>>> a1.save() |
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>>> a2 = Article(headline='Article 2', pub_date=datetime(2005, 7, 27), expire_date=datetime(2005, 7, 28)) |
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>>> a2.save() |
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>>> a3 = Article(headline='Article 3', pub_date=datetime(2005, 7, 27), expire_date=datetime(2005, 8, 27)) |
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>>> a3.save() |
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>>> a4 = Article(headline='Article 4', pub_date=datetime(2005, 7, 28), expire_date=datetime(2005, 7, 30)) |
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>>> a4.save() |
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# Get the latest Article. |
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>>> Article.objects.latest() |
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<Article: Article 4> |
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# Get the latest Article that matches certain filters. |
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>>> Article.objects.filter(pub_date__lt=datetime(2005, 7, 27)).latest() |
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<Article: Article 1> |
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# Pass a custom field name to latest() to change the field that's used to |
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# determine the latest object. |
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>>> Article.objects.latest('expire_date') |
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<Article: Article 1> |
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>>> Article.objects.filter(pub_date__gt=datetime(2005, 7, 26)).latest('expire_date') |
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<Article: Article 3> |
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# You can still use latest() with a model that doesn't have "get_latest_by" |
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# set -- just pass in the field name manually. |
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>>> p1 = Person(name='Ralph', birthday=datetime(1950, 1, 1)) |
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>>> p1.save() |
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>>> p2 = Person(name='Stephanie', birthday=datetime(1960, 2, 3)) |
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>>> p2.save() |
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>>> Person.objects.latest() |
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Traceback (most recent call last): |
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... |
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AssertionError: latest() requires either a field_name parameter or 'get_latest_by' in the model |
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>>> Person.objects.latest('birthday') |
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<Person: Stephanie> |
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"""} |