python - Django: adding an "Add new" button for a ForeignKey in a ModelForm

Question

TL;DR: How can I add an "Add new" button for a ForeignKey in a ModelForm?

Long version: I'm using Django 1.7 for a project. I have these two Models in my models.py

class Client(models.Model):
    name = models.CharField(max_length=100)

class Order(models.Model):
    code = models.IntegerField()
    client = models.ForeignKey(Client)

[some other non relevant fields are omitted]

I am using a ModelForm to populate the db with new orders, like this:

class OrderNewForm(forms.ModelForm):
    class Meta:
        model = Order

Django does quite a good job at adding a dropdown menu for the client field, populating it with entries taken from Client. Nevertheless, I'd like to have an "Add new client" link/button/whatever to add a brand new client at the same time I add a related Order.

Django admin does that automatically, adding a "+" button" that opens a popup, but I couldn't find an easy way to do that in a ModelForm like the one above. I read many questions here and links elsewhere, but nothing really helped me. Any idea about that?

Answer 1

I have solved it in a custom widget. I don't remember if I took parts from Django admin, or I have built from scratch.

So the form will be:

class OrderNewForm(forms.ModelForm):

   client = forms.ModelChoiceField(
       required=False,
       queryset=Client.objects.all(),
       widget=RelatedFieldWidgetCanAdd(Client, related_url="so_client_add")
                                )
   class Meta:
       model = Order
       fields = ('code', 'client')

And the widget, that renders the "+" button and link to the add popup in the admin interface or to a custom view you provice with the related_url argument is:

from django.core.urlresolvers import reverse
from django.utils.safestring import mark_safe
from django.forms import widgets
from django.conf import settings

class RelatedFieldWidgetCanAdd(widgets.Select):

    def __init__(self, related_model, related_url=None, *args, **kw):

        super(RelatedFieldWidgetCanAdd, self).__init__(*args, **kw)

        if not related_url:
            rel_to = related_model
            info = (rel_to._meta.app_label, rel_to._meta.object_name.lower())
            related_url = 'admin:%s_%s_add' % info

        # Be careful that here "reverse" is not allowed
        self.related_url = related_url

    def render(self, name, value, *args, **kwargs):
        self.related_url = reverse(self.related_url)
        output = [super(RelatedFieldWidgetCanAdd, self).render(name, value, *args, **kwargs)]
        output.append(u'<a href="%s" class="add-another" id="add_id_%s" onclick="return showAddAnotherPopup(this);"> ' % 
            (self.related_url, name))
        output.append(u'<img src="%sadmin/img/icon_addlink.gif" width="10" height="10" alt="%s"/></a>' % (settings.STATIC_URL, _('Add Another')))                                                                                                                               
       return mark_safe(u''.join(output))