mptt TreeNodeChoiceField filtered - django

Question

I am starting to work with django.
In my project I am using MPTT.
I have a fairly simple models.
Category: (the tree)
Product1: a reference and a foreign key to the category.
I added the root to the Category model, just to simplify the search for the base category for one specific product
models.py
class Category(MPTTModel):
name = models.CharField(max_length=200)
parent = TreeForeignKey('self', null=True, blank=True, related_name='children')
#property
def root(self):
return self.get_root().name
class Product1(models.Model):
ref = models.CharField(max_length=200, blank=True) #YVX2311
category = TreeForeignKey(Category)
admin.py
admin.site.register(Category, MPTTModelAdmin)
admin.site.register(Product)
What I would like is to modify the admin form, to be able to say something like.
models.ForeignKey(Category, limit_choices_to = {root : 'Some
Category for products1'})
Of course this is not possible, but it does illustrate what I want.
I want to be able to filter the TreeChoiseField to show only some branches based on a property on the model (root in this case).
Thanks

Answer 1

After much scrambling, I found a solution.
I do not think this is the best way to do it, but as far as I can see, it works.
I overloaded the mptt TreeNodeChoiceField and copied the TreeForeignKeyFiltered
In products, I changed the foreingkey for
category = TreeForeignKeyFiltered(Category, root = 'MotherBoard')
I added the root keyword to the TreeForeingKeyFiltered
class TreeForeignKeyFiltered(models.ForeignKey):
"""
Extends the foreign key, but uses mptt's ``TreeNodeChoiceField`` as
the default form field.
This is useful if you are creating models that need automatically
generated ModelForms to use the correct widgets.
"""
def __init__(self, *args, **kwargs):
self._root = kwargs.pop('root', None)
super(TreeForeignKeyFiltered, self).__init__(*args, **kwargs)
def formfield(self, **kwargs):
"""
Use MPTT's ``TreeNodeChoiceField``
"""
kwargs.setdefault('root', self._root)
kwargs.setdefault('form_class', TreeNodeChoiceFieldFiltered)
return super(TreeForeignKeyFiltered, self).formfield(**kwargs)
And finally I added the TreeNodeChoiceFieldFiltered as
class TreeNodeChoiceFieldFiltered(TreeNodeChoiceField):
def __init__(self, queryset, *args, **kwargs):
_root = kwargs.pop('root', None)
if _root is not None:
pid = None
for i in queryset:
if i.root.name == _root:
pid = i.tree_id
break
if pid is not None:
queryset = queryset.filter(tree_id = pid)
super(TreeNodeChoiceFieldFiltered, self).__init__(queryset, *args, **kwargs)
Now I can pass a keyword root to the foreingkey that will filter the posibilities in the admin form.
Again, I do not know if this is the best way to do it. Of course it can be cleaner....