django ModelForm "unique=True" - django

Question

I have a ModelForm where i give users a chance to create a new or edit an existing "Group" object. If "Edit" an existing is requested, i have it pre-populating the form data with the existing information. When the user goes to "Save" an edit on an existing object, i get this error:
"Group with this Name already exists."
How can i tell Django to "Update" the object instead of attempting to create a new one with the same name?
MODEL
class Analyst(models.Model):
first = models.CharField(max_length=32)
last = models.CharField(max_length=32)
def __unicode__(self):
return "%s, %s" % (self.last, self.first)
class Alias(models.Model):
alias = models.CharField(max_length=32)
def __unicode__(self):
return "%s" % (self.alias)
class Octet(models.Model):
num = models.IntegerField(max_length=3)
def __unicode__(self):
return "%s" % (self.num)
class Group(models.Model):
name = models.CharField(max_length=32, unique=True) #name of the group
octets = models.ManyToManyField(Octet, blank=True) #not required
aliases = models.ManyToManyField(Alias, blank=True) #not required
analyst = models.ForeignKey(Analyst) #analyst assigned to group, required
def __unicode__(self):
return "%s" % (self.name)
VIEW
class GroupEditForm(ModelForm):
class Meta:
model = Group
def index(request):
if request.method == 'GET':
groups = Group.objects.all().order_by('name')
return render_to_response('groups.html',
{ 'groups': groups, },
context_instance = RequestContext(request),
)
def edit(request):
if request.method == "POST":
form = GroupEditForm(instance = Group.objects.get(name=request.POST['name']))
elif request.method == "GET":
form = GroupEditForm()
return render_to_response('group_edit.html',
{ 'form': form, },
context_instance = RequestContext(request),
)
def save(request):
if request.method == "POST":
form = GroupEditForm(request.POST)
if form.is_valid():
form.save(commit=True)
return HttpResponseRedirect('/groups/')
return render_to_response('group_save.html',
{ 'test': form.errors, })

Answer 1

You have to get the extining group object in the save action and bound the form to it.
def save(request, id):
if request.method == "POST":
group = get_object_or_404(Group, pk=id)
form = GroupEditForm(request.POST, instance=group) # A form bound to the POST data
if form.is_valid():
form.save(commit=True)
return HttpResponseRedirect('/groups/')
return render_to_response('group_save.html',
{ 'test': form.errors, })