Django save_m2m() and excluded field - django

Question

UPDATE: I ended up creating a new forms.Form instead of using a ModelForm
In a ModelForm, I replaced a field by excluding it and adding a new one
with the same name, as shown below in AddRestaurantForm. When saving
the form with the code shown below, I get an error in form.save_m2m()
("Truncated incorrect DOUBLE value"), which seems to be due to the
function to attempt to save the tag field, while it is excluded.
Is the save_m2m() function supposed to save excluded fields?
Is there anything wrong in my code?
Thanks
Jul
(...)
new_restaurant = form.save(commit=False)
new_restaurant.city = city
new_restaurant.save()
tags = form.cleaned_data['tag']
if(tags!=''): tags=tags.split(',')
for t in tags:
tag, created = Tag.objects.get_or_create(name = t.strip())
tag.save()
new_restaurant.tag.add(tag)
new_restaurant.save()
form.save_m2m()
models.py
class Tag(models.Model):
name = models.CharField(max_length=100, unique=True)
class Restaurant(models.Model):
name = models.CharField(max_length=50)
city=models.ForeignKey(City)
category=models.ManyToManyField(Category)
tag=models.ManyToManyField(Tag, blank=True, null=True)
forms.py
class AddRestaurantForm(ModelForm):
name = forms.CharField(widget=forms.TextInput(attrs=classtext))
city = forms.CharField(widget=forms.TextInput(attrs=classtext), max_length=100)
tag = forms.CharField(widget=forms.TextInput(attrs=classtext), required=False)
class Meta:
model = Restaurant
exclude = ('city','tag')
Traceback:
File "/var/lib/python-support/python2.5/django/core/handlers/base.py"
in get_response
92. response = callback(request, *callback_args,
**callback_kwargs) File "/home/jul/atable/../atable/resto/views.py" in addRestaurant
498. form.save_m2m() File "/var/lib/python-support/python2.5/django/forms/models.py" in
save_m2m
75. f.save_form_data(instance, cleaned_data[f.name]) File "/var/lib/python-support/python2.5/django/db/models/fields/
related.py" in save_form_data
967. setattr(instance, self.attname, data) File "/var/lib/python-support/python2.5/django/db/models/fields/
related.py" in set
627. manager.add(*value) File "/var/lib/python-support/python2.5/django/db/models/fields/
related.py" in add
430. self._add_items(self.source_col_name, self.target_col_name, *objs) File
"/var/lib/python-support/python2.5/django/db/models/fields/
related.py" in _add_items
497. [self._pk_val] + list(new_ids)) File "/var/lib/python-support/python2.5/django/db/backends/util.py" in
execute
19. return self.cursor.execute(sql, params) File "/var/lib/python-support/python2.5/django/db/backends/mysql/
base.py" in execute
84. return self.cursor.execute(query, args) File "/var/lib/python-support/python2.5/MySQLdb/cursors.py" in execute
168. if not self._defer_warnings: self._warning_check() File "/var/lib/python-support/python2.5/MySQLdb/cursors.py" in
_warning_check
82. warn(w[-1], self.Warning, 3) File "/usr/lib/python2.5/warnings.py" in warn
62. globals) File "/usr/lib/python2.5/warnings.py" in warn_explicit
102. raise message
Exception Type: Warning at /restaurant/add/ Exception Value:
Truncated incorrect DOUBLE value: 'a'

Answer 1

I see you also posted this same question to Django-users. I'll copy the answer I've posted there:
Firstly, it is no use just giving the name of the error. Errors come
with tracebacks, for good reason: they allow us to see exactly where
the error is occurring, and the context.
Anyway, in your case, there doesn't seem to be any need to use
save_m2m. The documentation states:
"Calling save_m2m() is only required if you use save(commit=False)"
In your case, you've already saved the form to get the new_restaurant
instance, and you're adding tags to that instance with no problem. The
last two calls, to new_restaurant.save() and form.save_m2m(), are unnecessary.

Answer 2

You don't need either of the last two "save" calls. Your tags relation will be implicitly saved by virtue of the add(). I'd just drop those from the code.