Best practice for Notifications on a single model that can be created multiple different ways.

[diericx]

Hey, I've run into a little design snag that I'd love to get some advice on. I'll explain my situation real quick for some context.
I have these models:

User
Page
Post
Comment
  commentable: polymorphic{Page,Post}
  parent: Comment

And this notification controller which I'm unsure about.

CommentNotification
  param :comment

A user can create/follow (meaning they get notifications for) a Page and a Post and will get notifications for any replies to their comments. This means a comment can be created 3 different ways, and should have a different url and message for each one. I am currently switching on these cases within the controller.

Does this sound like a solid plan? I considered having different controllers for each Notification case (e.g. NestedCommentNotification, PageCommentNotification, PostCommentNotification). It seems like that would then add a lot of unnecessary complexity when trying to get total notification counts and marking notifications as read, and a lot of repetition.

I've also considered I may be stretching the responsibilities of the Comment model too thin trying to apply it to both Pages and Posts, but the discussion requirements were the exact same for each case so it made sense to simply use the Comment model in both cases.

I was wondering if anyone else has run into something similar and has any insight. I haven't completely built out the functionality above due to my concerns, but the example below should have enough to display what I'm talking about above.

class CommentNotification < Noticed::Base
  deliver_by :database

  param :comment

  # haven't applied the switch functionality here yet but you get the idea that I would be switching on each case
  # to produce/use a different message.
  def message
    comment = params[:comment]
    if comment.is_nested
        t(".message", parent_user_display_name: params[:comment].parent.user.display_name)
    end
  end

  def url
    comment = params[:comment]
    case comment.commentable
    when Post
      post = comment.commentable
      return post_path(post.id)
    when Page
      page = comment.commentable
      return wiki_page_path(page.wiki.id, page.id)
    end
  end
end

[excid3]

Great question! You can really set it up however you like.

For polymorphic comments, I've actually setup namespaced controllers and include shared functionality with a concern. This makes it so you can branch out as necessary if you want comments to work slightly different for one model than another. Most of the time I don't override anything though.

In your url method, the only non-standard thing I see is the wiki_page_path that makes that conditional required.

There should be a way to override to_param or something on your Page model to automatically include the Wiki ID. I believe something like this should work:

class Page
  def to_param
    "/wikis/#{wiki.id}/pages/#{id}"
  end
end

That would allow you to treat all the commentable objects as the same in the url method:

def url
  url_for([params[:comment].commentable])
end