class Part < ActiveRecord::Base has_many :lots has_many :components # or, maybe not end
class Lot < ActiveRecord::Base belongs_to :part has_many :components end class Component < ActiveRecord::Base belongs_to :part # or, maybe not belongs_to :lot end In my domain, a "lot" of "components" has a part number (which I represent in RoR as a #belongs_to relationship, even though the term "belongs_to" is somewhat misleading). Each component in the lot has a part number which is the same as the part number for the entire lot. What is the best way to ensure that this consistency is maintained? That is, that all parts in a lot reference the same part number as the lot itself. One way to ensure the consistency is to remove the "part_id" column from the component table and to reference a components part number through the lot association, i.e. mycomponent.lot.part.number. The problem is, sometimes I want to look at all of the parts that have a given part number, and the only way I can see to do that is to collect all of the lots with a given part number and then collect all of the components in each of the lots, using something like: mypart.lots.map(&:components).flatten. Unfortunately, that returns an array of components instead of the dynamic finder that would be returned by mypart.components. A second way to ensure the consistency is to add validations to the Lot and/or Component models. I could do that, but I have been advised elsewhere that validations are best when augmented by database constraints. (See http://groups.google.com/group/rubyonrails-talk/browse_thread/thread/3b023e81df58619d, if you are interested). Is there some database agnostic way to add this sort of constraint? Or is there some other mechanism to implement this? --wpd --~--~---------~--~----~------------~-------~--~----~ 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 rubyonrails-talk@googlegroups.com To unsubscribe from this group, send email to rubyonrails-talk+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
