My mistake not making it clear enough. Actually they have some attributes.
Let's say, A has a simple attribute called A.name and C also has a attribute C.name. Then A has_many C, which means C.a_id exists. In my case, my requirement is that if users enter C2.name、 C3.name and C4.name, I should show them A1.name or whatever attributes A might have that needs to be displayed. Anyway, thanks for your reply. On Wednesday, January 13, 2016 at 4:47:35 PM UTC+8, Colin Law wrote: > > On 13 January 2016 at 07:22, Lei Zhang <ray.zh...@gmail.com <javascript:>> > wrote: > > I am going to implement a small and simple search feature in my project. > But > > got a question about the scenario I have right now. So hope to get some > tips > > from here. > > > > First of all, this is a rails app. > > > > There are two models, A and C. > > > > A has_many C. > > > > That's to say, it might have some situation like this: > > > > A1 related to C1, C2, C3, C4 > > A2 related to C2, C3, C4, C5 > > A3 related to C2, C3, C4, C8 > > A4 related to C3, C4, C8, C9 > > A5 related to C4, C8, C9, C20 > > For that you need A has_and_belongs_many C, or (my preferred solution) > introduce a join model/table and use has_many through. You can't use > has_many as that would require > C belongs_to A > which is not correct. > > > > > Use C2, C3, C4 as keyword, I can get A1, A2, A3 > > Use C4, C8, C9 as keyword, I can get A4, A5 > > > > I consider that this can be done by using something straightforward like > > A.Cs.includes?(C2,C3,C4). > > > > But that requires an iteration of A. And I concern that it would have > some > > performance issue. > > > > Any advice or idea about this requirement ? > > I don't understand exactly what your requirement is. in particular > what do you mean by "use C2, C3, C4 as keyword", when each of the Cs > is a record in the db. > If you are trying to get all the As related to records C2, C3 and C4 > then that is something like > (c2.as + c3.as +c4.as).uniq > though that may not be the most efficient way. > > Colin > -- You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To unsubscribe from this group and stop receiving emails from it, send an email to rubyonrails-talk+unsubscr...@googlegroups.com. To post to this group, send email to rubyonrails-talk@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rubyonrails-talk/4c2dfaeb-604a-4550-b799-71d45fdfddfe%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
