#14018: Introduce class_plural %-substitution placeholder for related_name of
ForeignKey/ManyToManyField
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Reporter: puxlit |
Owner: nobody
Status: new |
Milestone: 1.3
Component: Database layer (models, ORM) |
Version: SVN
Keywords: related_name, ManyToManyField, ForeignKey, abstract base class |
Stage: Unreviewed
Has_patch: 1 |
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Django 1.2 [http://docs.djangoproject.com/en/dev/topics/db/models/#be-
careful-with-related-name introduced] two %-substitution placeholders,
`%(class)s` and `%(app_label)s`, to work around uniqueness issues when a
custom `related_name` for a `ForeignKey` or `ManyToManyField` defined in
an abstract base class is inherited by multiple child classes.
Quoting from [http://docs.djangoproject.com/en/dev/topics/db/models/#many-
to-many-relationships Django's models documentation], "''It's suggested
![...] that the name of a `ManyToManyField` ![...] be a plural describing
the set of related model objects.''" Given the nature of a
`ManyToManyField`, it may be preferable to reciprocate this pluralized
field naming style through `related_name`. By introducing a third
%-substitution placeholder, `%(class_plural)s`, this can be accomplished.
Consider the following snippet:
{{{
#!python
class Tag(models.Model):
slug = models.SlugField(max_length=63, unique=True)
class Post(models.Model):
slug = models.SlugField(max_length=127, unique=True)
tags = models.ManyToManyField(Tag, related_name='%(class_plural)s') #
docs suggest related_name='%(app_label)s_%(class)s_related'
class Meta:
abstract = True
class Entry(Post):
title = models.CharField(max_length=255)
content = models.TextField()
class Meta:
verbose_name_plural = 'entries'
class Event(Post):
summary = models.CharField(max_length=255)
start_date = models.DateTimeField()
}}}
Arguably, `tag.entries` and `tag.events` are more semantic than either
`tag.entry_set` and `tag.event_set` or `tag.appname_entry_related` and
`tag.appname_event_related`.
Ultimately, the introduction of a `%(class_plural)s` %-substitution
placeholder provides greater flexibility when designing models with
abstract base classes and ForeignKeys or ManyToManyFields.
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Ticket URL: <http://code.djangoproject.com/ticket/14018>
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