Re: [Rails] Auto numbering of childs for a parent

> I have a Author model and Book model
>
> # field_names => [id, name]
> class Author < AR::Base
> has_many :books
> end
>
> # field_names => [id, name]
> class Book < AR::Base
> belong_to :author,
> attr_accessor :serial_number
> end
>
> Now for example I have inserted two books BOOK1(id:101) and
> BOOK2(id:102) for a author AUTHOR1(id:30)
>
> Now when I load the author with books like Author.find_by_id
> (30, :include => :books)
>
> I want a way to set the serial_number incrementally for each Book
> according to the order of their ID field (or may be any other logic).
> In above example BOOK1(serial_number:1) and BOOK2(serial_number:2)
>
> Some more requirements:
> I need it to work even when i find Book.find_by_id(102) and expecting
> the serial_number to set 2
>
> Any better recommendation?

You might look into acts_as_list at http://github.com/rails/
acts_as_list.

-philip