ruby on rails - How to associate a model with a model within a model? -

when user likes comment create_notification triggered in commet_like.rb:

class commentlike < activerecord::base   after_create :create_notification   has_many :notifications   belongs_to :user   belongs_to :comment   validates :user, uniqueness: { scope: :comment }   belongs_to :liker, class_name: 'user', foreign_key: :user_id   belongs_to :liked_comment, class_name: 'comment', foreign_key: :comment_id  private    def create_notification     notifications.create(       comment_like: self,       comment:      comment,       user:         comment.user,             read:         false     )   end end 

i'm trying work in notifications index:

  <% if notification.comment_like_id %>     <% if notification.goal_id %>         liked <%= link_to "your comment", notification_goal_path(notification, notification.goal_id) %>     <% elsif notification.habit_id %>         liked <%= link_to "your comment", notification_habit_path(notification, notification.habit_id) %>     <% elsif notification.quantified_id %>         liked <%= link_to "your comment", notification_quantified_path(notification, notification.quantified_id) %>     <% elsif notification.valuation_id %>         liked <%= link_to "your comment", notification_valuation_path(notification, notification.valuation_id) %>     <% end %>   <% end %> 

but problem each of conditionals nil comment_like therefore notification showing blank.

as can see here though commentlike associated comment, in example gives comment_id: 1 , comment_id: 1 has valuation_id: 1.

[1] commentlike.find(1)  id: 1,  user_id: 1,  comment_id: 1, [2] comment.find(1)  id: 1,  content: "test",  goal_id: nil,  habit_id: nil,  valuation_id: 1,  quantified_id: nil,  commentable_id: nil,  commentable_type: nil,  user_id: 1,  likes: 1> 

how can use association make right conditional show under comment_like_id according comment's association 4 other models?

notifications_controller

  def index     @notifications = current_user.notifications     @notifications.each |notification|       notification.update_attribute(:read, true)      end   end 

comment.rb

class comment < activerecord::base   after_create :create_notification   has_many :notifications   has_many :comment_likes      has_many :likers, through: :comment_likes, class_name: 'user', source: :liker   belongs_to :habit   belongs_to :quantified   belongs_to :valuation   belongs_to :goal   belongs_to :user  private    def create_notification     author =        if goal         goal.user       elsif habit        habit.user       elsif quantified         quantified.user       elsif valuation         valuation.user       end     notifications.create(       comment:      self,       habit:        habit,       quantified:   quantified,       goal:         goal,       valuation:    valuation,       user:         author,             read:         false     )   end end 

please let me know if need further explanation or code :-]

forgive me, since don't know habit, quantified, etc are, code makes things commented on, therefore seems should using polymorphic association.

class comment < activerecord::base   belongs_to :commentable, polymorphic: true   has_many :notifications   after_create :notify_user    def notify_user     self.notifications.create user: commentable.user   end end  class habit < activerecord::base   has_many :comments, as: :commentable end  class notification < activerecord::base   belongs_to :comment   belongs_to :user   delegate :commentable, to: :comment end 

here, using polymorphic relationship, simplify quite bit. further, can use polymorphic route helper

<%= link_to "your comment", polymorphic_url(notification, commentable) %> 

hope helps point in right direction