ManyToMany with related_name?
I'm trying to create a model that relates back to itself with a ManyToManyField. Here's my model:class PressRun(models.Model): starttime = models.DateTimeField(db_index=True) endtime = models.DateTimeField
(validator_list=[endAfterStartValidator]) name = models.CharField(maxlength=100,blank=True) recurringitem = models.ForeignKey(RecurringPressRun,blank=True,null=True) edition = models.IntegerField(choices=EDITION_CHOICES,blank=True,null=True)
press_id = models.IntegerField(choices=PRESS_CHOICES,blank=True,default=1) insert_into = models.ManyToManyField('self', null=True, blank=True, related_name='insert')
The problem is that the model doesn't seem to use the related_name option. PressRun objects have an insert_into property, but no insert property. I'm actually trying to say that the result of a PressRun can be "inserted" into another PressRun, but I don't want to make a separate object (like PressRunInsert or something). I'd like to use a simple ManyToMany, but the objects don't have a distinction between "inserted into" and "insert of".
Does that make sense?Dave
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Re: ManyToMany with related_name?
On 4/13/06, Dave St.Germain <[EMAIL PROTECTED]> wrote:
I'm trying to create a model that relates back to itself with a ManyToManyField. Here's my model:I'd like to use a simple ManyToMany, but the objects don't have a distinction between "inserted into" and "insert of".
Does that make sense?Yup. The problem here is that Django assumes that if you have a ManyToMany field on self, then the relationship is symmetrical: for example:class Person:
friend = ManyToManyField('self')If I am your friend, then presumably you are my friend. To avoid confusion, the reverse representation of the relationship (person_set, or whatever related_name specifies) is not added to instances of Person.
Obviously, there are some use cases (such as yours) where this is not the case - to handle these, you need to set symmetrical=False:
insert_into = models.ManyToManyField('self',
null=True,
blank=True,
related_name='insert'
symmetrical=False)
This will add the related_name member on the related object, and will be a distinct set; adding to PressRun.insert_into is not the same as adding to PressRun.insertHope this helps,Russ Magee %-)
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