On 16 May 2010 06:21, Albus Dumbledore <[email protected]> wrote: > Well. I am having trouble understanding how acts_as_list works. I do not > quite comprehend what the table schema for the example given by DHH must > be: > > [code] > > class TodoList < ActiveRecord::Base > has_many :todo_items, :order => "position" > end > > class TodoItem < ActiveRecord::Base > belongs_to :todo_list > acts_as_list :scope => :todo_list > end > > [/code] > > More precisely I wonder where should the `position` column go? To me it > looks like it should go with the table having the foreign keys, i.e. > `todo_items` table. Then it would seem that there would be no need for a > `todo_lists` table, right? So it would be all about the todo_items > table.
Yes; the position column goes on the table you want ordered. The purpose of the todo_list table is to allow there to be more than one list of items (if you want one). The "scope" field is a way of identifying what separates the lists in the items table. So if every user needs a list, then you can scope by user; if you're only having one list of the items, then there's no need for a scope - just position. > It's scope that is bothering me. Firstly we can have our rows grouped > by a foreign key (which seems trivial enough). However, what happens if > it is a polymorphic reference, i.e. we need to use two columns to select > a unique row? Right.... your posting is suffering a little "feature creep" at the moment. If you post what the limits are of the real problem you have, then people can suggest solutions. If you have a complicated data structure, then post some of the model code so we can all get our heads around it. > > Thank you! > -- > Posted via http://www.ruby-forum.com/. > > -- > You received this message because you are subscribed to the Google Groups > "Ruby on Rails: Talk" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]. > For more options, visit this group at > http://groups.google.com/group/rubyonrails-talk?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.
