On Fri, 2009-01-09 at 03:33 -0800, rabbi wrote:
> Is there a way to specify a constraint on a model ManyToMany
> relationship?
>
> For example, if I wanted to define an Animal model that has a field
> which specifies which other animals it eats and I wanted to limited
> these animals_I_eat relationships to animals who's specie_name starts
> with "x", how would I do this?
>
> E.g.
>
> class Animal(models.Model):
> specie_name = models.CharField(max_length=50)
> animals_I_eat = models.ManyToManyField('self',blank=True)
> #where animals_I_eat.specie_name starts with "x"
>
> This is probably a very bad example, but I hope you get what I'm
> trying to say
Do you want this constraint to be enforced for every piece of data that
is inserted? If so, you can't do that yet (sorry!). It requires what
we're calling model-aware validation, at a minimum, and that's something
that we're working on for Django 1.1 (in fact, right this minute, I'm
reviewing some of that code). Essentially, that means form-like
validation for models.
Or are you asking how to filter out all the Animals that satisfy that
constraint?
Regards,
Malcolm
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