Exception message is worded poorly (backwards)
|Reported by:||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:||master|
|Severity:||Keywords:||models many-to-many manytomany m2m exception primary key pk|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
This occurs with recent SVN checkout.
(trimmed) example models:
class Tag(models.Model): name = models.CharField(max_length=127, unique=True) class Image(models.Model): tags = models.ManyToManyField(Tag)
code which bombs:
t = Tag(name='foo') t.save() i = Image() i.tags.add(t) #Bombs here because i doesn't have a pk
Traceback File "reloadDB.py", line 73, in ? i.tags.add(t) File "/usr/lib/python2.4/site-packages/django/db/models/fields/related.py", line 485, in __get__ target_col_name=qn(self.field.m2m_reverse_name()) File "/usr/lib/python2.4/site-packages/django/db/models/fields/related.py", line 317, in __init__ raise ValueError("%r instance needs to have a primary key value before a many-to-many relationship can be used." % model) ValueError: <class 'eTrain.models.Tag'> instance needs to have a primary key value before a many-to-many relationship can be used.
The error should indicate the <class 'eTrain.models.Image'> instance doesn't have pk... I'm not sure how to get at this as superclass doesn't seem to have the model attribute set.