CODEWITHSUNDEEP
ruby-on-rails-3activerecordpolymorphic-associations
Ashley
Ashley

Reputation: 2318

Filtering associated polymorphic models

I have Favorite model which allows Entries and Feeds to be saved by users.

class User < ActiveRecord::Base
   has_many :favorites
   has_many :favorite_feeds, :through =>  :favorites, :source => :favorable, :source_type => "Feed"
   has_many :favorite_entries, :through =>  :favorites, :source => :favorable, :source_type => "Entry"
 end

 class Favorite < ActiveRecord::Base
   belongs_to :user
   belongs_to :favorable, :polymorphic => true
   attr_accessible :user, :favorable
 end

 class Feed < ActiveRecord::Base
   has_many :favorites, :as => :favorable
   has_many :fans, :through => :favorites, :source => :user
 end

 class Entry < ActiveRecord::Base
   has_many :favorites, :as => :favorable
   has_many :fans, :through => :favorites, :source => :user
 end

I now need to display ALL Entries on a page and indicate whether the current_user has added each Entry as a favourite. At the moment calling @entry.fans is fetching every User from the database, which is inefficient. I need a way of filtering this call to only fetch favorites that belong to the current_user since I don't need any of the other records.

I can do this in memory in my controller, but I'm thinking there is a way to simply select the current_users favorites and join it to the Entries model using Active::Record.

Thanks.

Upvotes: 0

Views: 449

Answers (1)

MrTheWalrus
MrTheWalrus

Reputation: 9700

Controller:

@entries = Entry.all
@user_favorite_entry_ids = current_user.favorite_entries.pluck(:id)

View:

<% @entries.each do |entry| %>
<%= @entry.id %>: <%= @entry.id.in?(@user_favorite_entry_ids) ? 'favorite of current user' : 'not' %>
<% end %>

Or, if you really like doing things in the database:

@entries = Entry.select('entries.*, count(favorites.id) as current_user_favorite').joins("left join favorites on favorites.favorable_id = entries.id and favorites.favorable_type = 'Entry' and favorites.user_id = #{current_user.id}")

and then:

<% @entries.each do |entry| %>
  <%= @entry.id %>: <%= (@entry.current_user_favorite.to_i > 0) ? 'favorite of current user' : 'not' %>
<% end %>

Upvotes: 1

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