How to use Link_to with nested resources

Question

I am a totally newbie in Rails.

I have created a web application, I can access through /posts/123/comments/ or /posts/123/comments/new, but i don't know how to use link_to in the index view to show a concrete comment, when i try to link it, appears "no route" or "undefined symbol".

I have a nested have_many relation between posts and comments defined in the models and in the routes.rb and post_comments GET /posts/:post_id/sensors(.:format) comments#index appears when I execute rake routes.

How I can do it?

Answer 1

After trying all of the answers it didnt completely work, but i found a way to resolve it. In a first moment, I used

post_comments_url(@post,comment)

where comment is the item inside a @post.each.

It generates a "strange" route, using . instead / like "post/34/comments.2", i fixed it using the singular form:

post_comment_url(@post,comment)

Thanks for helping!

Answer 2

If you have defined nested resources (and of course your models Comment and Post are associated)

resources :posts do
 resources :comments
end

You can link a comment as following

<!-- /posts/:post_id/comments/:id -->
<%= link_to 'Show', [@comment.post, @comment] %>

I've written a full example of nested resources in a past blog post

Answer 3

Get method name from the first column of

   rake routes

And pass the ids accordingly. And of course suffix the method name with _path ir _url To know more, visit the Rails guide

Answer 4

Additionally to the answer of toch, you can debug your link_to call with help of the Rails console.

For this, you need to load the view helpers in the console:

irb(main):001:0> include ActionView::Helpers::UrlHelper
=> Object
irb(main):002:0> helper.link_to "posts", app.posts_path
=> "<a href=\"/posts\">foo</a>"

Another tool, similar to Rake routes for route debugging is: https://github.com/schneems/sextant