How to use autocompleteselect widget in a modelform

Question

I know there is a new feature in Django 2.0, which is AutocompleteSelect widget in ModelAdmin. I am trying to use it in my custom modelForm but just failed.

Tried like this

#unit is the foreign key to the incident

class AccountForm(forms.ModelForm):
    class Meta:
        model = Invoice
        ...
        ...
        widgets = {       'incident':widgets.AutocompleteSelect(Invoice._meta.get_field('incident').remote_field, admin.site)
        }
        ...

#Invoice model

class Invoice(models.Model):
    ...
    incident = models.ForeignKey(Unit, on_delete=models.CASCADE,null=True)
    ...

Hope anyone can help me. Thanks

Answer 1

The AutocompleteSelect widget will not work outside of the admin site. If you are using AccountForm in admin site you can use the following code:

class AccountForm(forms.ModelForm):
    ...
    incident = forms.ModelChoiceField(
                 queryset= Unit.objects.all(),
                 widget=AutocompleteSelect(Invoice.incident.field.remote_field, admin.site),
               )
    ...
    class Meta:
        model = Invoice
        fields = [
            'incident',
            ...
        ]

@admin.register(Invoice)
class InvoiceAdmin(admin.ModelAdmin):
    form = AccountForm

Answer 2

AutocompleteSelect has 2 required args, rel and admin_site. The rel is used to extract the model used to query the data from and relates to an attribute on a ForeignKey or ManyToManyField. Since I wanted to use this on a field that wasn't actually a ForeignKey, I needed to override a few things to make it work:

class ClientAutocompleteSelect(AutocompleteSelect):
    def get_url(self):
        model = Client
        return reverse(self.url_name % (self.admin_site.name, model._meta.app_label, model._meta.model_name))

class ClientChoiceField(forms.ModelChoiceField):
    def __init__(self, queryset=None, widget=None, **kwargs):
        if queryset is None:
            queryset = Client.objects.all()
        if widget is None:
            widget = ClientAutocompleteSelect(None, admin.site)  # pass `None` for `rel`
        super().__init__(queryset, widget=widget, **kwargs)

    def to_python(self, value):
        return value  # just return the client_id and not a Client object

class MyAdminForm(forms.ModelForm):
    client_id=ClientChoiceField()

    ...

This requires that the end user has admin read access to the autocomplete endpoint of the model being queried. You may be able to do more hacking to change that get_url and use your own endpoint to give search results, though.