# About nested resources **URL:** \ **Category:** Rails\ **Created:** [February 21, 2009, 6:53am UTC](https://www.ruby-forum.com/t/about-nested-resources/160943 "2009-02-21T06:53:57Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![difei](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a4c791/32.png) [@difei](https://www.ruby-forum.com/u/difei)\ **Post date:** [February 21, 2009, 6:53am UTC](https://www.ruby-forum.com/t/about-nested-resources/160943/1 "2009-02-21T06:53:57Z")
Hi all, I have several resources: map.resources :articles, :has\_many =\> [:comments] map.resources :movies, :has\_many =\> [:comments] map.resources :photos, :has\_many =\> [:comments] all of them have a nested resource named comments, new comments are able to be created by POST to URLs like article\_comments\_url. My problem is, when I’m in the comments\_controller, how can I know which resource this comment belongs to? By reading the params? I think this is not decent, are there any better ways? Thanks in advance! Cheers, Difei ---
**Author:** ![difei](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a4c791/32.png) [@difei](https://www.ruby-forum.com/u/difei)\ **Post date:** [February 21, 2009, 2:29pm UTC](https://www.ruby-forum.com/t/about-nested-resources/160943/2 "2009-02-21T14:29:50Z")
Difei, If a comment only belongs to either an article, movie or a photo (never more than one) you could add methods in the model to determine which it is for. For example: class Comment def article\_comment? !article\_id.nil? end end @comment.article\_comment? will return true if this is a comment for an article and false if not. You could render your view accordingly for each type of comment. Hope that helps? On Feb 21, 5:53 am, Difei Z. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![difei](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a4c791/32.png) [@difei](https://www.ruby-forum.com/u/difei)\ **Post date:** [February 22, 2009, 4:27pm UTC](https://www.ruby-forum.com/t/about-nested-resources/160943/3 "2009-02-22T16:27:52Z")
Gavin wrote: > Difei, > > If a comment only belongs to either an article, movie or a photo > (never more than one) you could add methods in the model to determine > which it is for. > > For example: > > class Comment > > def article\_comment? > !article\_id.nil? > end > end > > @comment.article\_comment? will return true if this is a comment for an > article and false if not. > > You could render your view accordingly for each type of comment. > > Hope that helps? Hi Garvin, but your way is to decide the father of an existed comment. if I just received POST to /articles/:article\_id/comments/:comment\_id, and I have a: @comment = Comment.new(params[:comment]), how could I tell this @comment is for article but not photo? By test params? Thanks. > On Feb 21, 5:53�am, Difei Z. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![difei](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a4c791/32.png) [@difei](https://www.ruby-forum.com/u/difei)\ **Post date:** [February 22, 2009, 11:26pm UTC](https://www.ruby-forum.com/t/about-nested-resources/160943/4 "2009-02-22T23:26:56Z")
That seems like a fine solution. what about just creating three different types of comments, article\_comment, movie\_comment, photo\_comment? I’m not necessarily advocating for this, but it’s an option, and it may be better. That way, you don’t need the functions at all. and it should help keep your controllers & views simple. There is in some sense a problem of code duplication between the three comment resources, but you may be able to DRY this up with helper methods. -Gabe ---
**Author:** ![difei](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a4c791/32.png) [@difei](https://www.ruby-forum.com/u/difei)\ **Post date:** [February 22, 2009, 6:12pm UTC](https://www.ruby-forum.com/t/about-nested-resources/160943/5 "2009-02-22T18:12:15Z")
Ah - I think I understand now. I would add a column to the comments table called ‘kind’ (as in, ‘kind of comment’) The column should be an integer column with limit 1. Then assign a different integer value to determine what kind of comment it is. i.e., 1 = article 2 = photo 3 = movie When you creating a new comment, simply check the value of this integer and redirect accordingly. Does that help? On Feb 22, 3:27 pm, Difei Z. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) ---
**Author:** ![difei](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a4c791/32.png) [@difei](https://www.ruby-forum.com/u/difei)\ **Post date:** [February 22, 2009, 11:32pm UTC](https://www.ruby-forum.com/t/about-nested-resources/160943/6 "2009-02-22T23:32:48Z")
Hypothetically, if one were to create three different types of comment would you just create a Comment model and then three other models that were subclasses? I’ve never played with subclasses in a rails app (other than the ones specified by rails) so I’m curious as to which whether this would be the way to do it? Gav ---
**Author:** ![difei](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/a4c791/32.png) [@difei](https://www.ruby-forum.com/u/difei)\ **Post date:** [February 23, 2009, 5:35am UTC](https://www.ruby-forum.com/t/about-nested-resources/160943/7 "2009-02-23T05:35:12Z")
Hi all, Since my commentable resources are not too many, I decided to do something like this in the comment controller: before\_filter: find\_resource private def find\_resource if params[:article\_id] @resource = Article.find(params[:article\_id]) elsif params[:photo\_id] @resource = Photo.find(params[:article\_id]) end end Thank y’all, Difei