It also depends how optimal your SQL ends up. Blog: http://random8.zenunit.com/ Learn rails: http://sensei.zenunit.com/
On 01/04/2009, at 11:28 PM, Harold <[email protected]> wrote: > > I think this is a common 'dilemma' that comes across every now and > then. "Which model should I ask for this information"? I also think > there's no right answer. But here's my two cents: > > In your case, you want to know which a product was purchased by a > user, so the question could go both ways: Did a user purchase this > product, or was this product purchased by the user. I think it depends > on your views and controllers, in other words, what is the main object > you find out the relationship about? If you're on a user view and want > to list purchased products, you might just ask @user.orders.each { |o| > o.products }.flatten (or some such thing). Similarly, > @product.orders.each { |o| o.user }.flatten would give you all users > who purchased that product. (this is all making some assumptions about > your relationships). > > In either case, you are working with either an instance of User, or an > instance of Product, so I think that that this should not be a class > method, but an instance method. > > Same goes when you're already dealing with a user instance and a > product instance and you want to find out if that relationship exists, > which is more to the point of your original post. How about an > instance method on the User class called has_purchased?: > > @user.has_purchased?(@product) => true #or false > > > Here's a stab at that method... > #class User < AR:Base > def has_purchased?(product) > !self.orders.products.find_by_id(product).nil? > end > > About joins, I think they are absolutely needed. Some models are more > "self contained" than others, but since you're working with a > relational model, it is natural that some models depend on others, and > using :joins or :include in your finders makes life easier in many > cases... > > > On Apr 1, 5:05 am, Fernando Perez <[email protected]> > wrote: >> I think the problem lies in the ability for the DB to perform a join >> across multiple tables which in fact breaks encapsulation! >> >> Maybe I should break down my DB query that uses joins into smaller >> queries. The code is obviously less efficient, but it's more >> maintainable, as each model is only concerned with its own stuff, and >> therefore I don't have to make edits across various models just >> because >> I changed the name or type of attributes in a single model. >> >> Using joins across multiple models doesn't feel right anymore. >> -- >> Posted viahttp://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 -~----------~----~----~----~------~----~------~--~---
