Django Admin: OneToOne Relation as an Inline?

Question

I am putting together the admin for a satchmo application. Satchmo uses OneToOne relations to extend the base Product model, and I'd like to edit it all on one page.

It is possible to have a OneToOne relation as an Inline? If not, what is the best way to add a few fields to a given page of my admin that will eventually be saved into the OneToOne relation?

for example:

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

class MyProduct(models.Model):
    product = models.OneToOne(Product)
    ...

I tried this for my admin but it does not work, and seems to expect a Foreign Key:

class ProductInline(admin.StackedInline):
    model = Product
    fields = ('name',)

class MyProductAdmin(admin.ModelAdmin):
    inlines = (AlbumProductInline,)

admin.site.register(MyProduct, MyProductAdmin)

Which throws this error: <class 'satchmo.product.models.Product'> has no ForeignKey to <class 'my_app.models.MyProduct'>

Is the only way to do this a Custom Form?

edit: Just tried the following code to add the fields directly... also does not work:

class AlbumAdmin(admin.ModelAdmin):
    fields = ('product__name',)

Answer 1

It's perfectly possible to use an inline for a OneToOne relationship. However, the actual field defining the relationship has to be on the inline model, not the parent one - in just the same way as for a ForeignKey. Switch it over and it will work.

Edit after comment: you say the parent model is already registered with the admin: then unregister it and re-register.

from original.satchmo.admin import ProductAdmin

class MyProductInline(admin.StackedInline):
    model = MyProduct

class ExtendedProductAdmin(ProductAdmin):
    inlines = ProductAdmin.inlines + (MyProductInline,)

admin.site.unregister(Product)
admin.site.register(Product, ExtendedProductAdmin)

Answer 2

Referring to the last question, what would be the best solution for multiple sub-types. E.g class Product with sub-type class Book and sub-type class CD. The way shown here you would have to edit a product the general items plus the sub-type items for book AND the sub-type items for CD. So even if you only want to add a book you also get the fields for CD. If you add a sub-type e.g. DVD, you get three sub-type field groups, while you actually only want one sub-type group, in the mentioned example: books.