#2653 closed defect (fixed)
multiple manytomanyfield on self causes complaint in manage.py
Reported by: | Owned by: | Russell Keith-Magee | |
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Component: | Core (Other) | Version: | dev |
Severity: | normal | Keywords: | |
Cc: | Triage Stage: | Unreviewed | |
Has patch: | no | Needs documentation: | no |
Needs tests: | no | Patch needs improvement: | no |
Easy pickings: | no | UI/UX: | no |
Description
Consider:
class Foo(models.Model): related = models.ManyToManyField('self') suggestions = models.ManyToManyField('self')
Both relations should be symmetrical. If A suggests B, B suggests A (for this code
base anyways).
What I expected to happen is adding B to A would add A to B. Instead I get:
app.foo: Accessor for m2m field 'menu_suggestions' clashes with related
m2m field 'Foo.foo_set'. Add a related_name argument to the definition
for 'suggestions'.
app.foo: Accessor for m2m field 'related' clashes with related m2m field
'Foo.foo_set'. Add a related_name argument to the definition for 'related'.
Doesn't matter whether I set symmetrical to false or true.
The confusion stems from model-api.txt which states:
``symmetrical`` Only used in the definition of ManyToManyFields on self. Consider the following model: class Person(models.Model): friends = models.ManyToManyField("self") When Django processes this model, it identifies that it has a ``ManyToManyField`` on itself, and as a result, it doesn't add a ``person_set`` attribute to the ``Person`` class. Instead, the ``ManyToManyField`` is assumed to be symmetrical -- that is, if I am your friend, then you are my friend. If you do not want symmetry in ``ManyToMany`` relationships with ``self``, set ``symmetrical`` to ``False``. This will force Django to add the descriptor for the reverse relationship, allowing ``ManyToMany`` relationships to be non-symmetrical.
Change History (4)
comment:1 by , 18 years ago
Owner: | changed from | to
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comment:2 by , 18 years ago
Status: | new → assigned |
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comment:3 by , 18 years ago
Resolution: | → fixed |
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Status: | assigned → closed |
(In [3734]) Fixes #2653 -- Modified related field utility methods to return None as the related name for symmetrical m2m fields on self. Updated validators and unit tests to account for the new behavior.