Use transaction when favoriting to prevent post from being half-favorited

app/models/favorite.rb

@@ -12,26 +12,30 @@ class Favorite < ActiveRecord::Base
   end
 
   def self.add(post, user)
-    return if Favorite.for_user(user.id).where(:user_id => user.id, :post_id => post.id).exists?
-    Favorite.create(:user_id => user.id, :post_id => post.id)
-    Post.update_all("fav_count = fav_count + 1", {:id => post.id})
-    Post.update_all("score = score + 1", {:id => post.id}) if user.is_gold?
-    post.append_user_to_fav_string(user.id)
-    User.update_all("favorite_count = favorite_count + 1", {:id => user.id})
-    user.favorite_count += 1
-    # post.fav_count += 1 # this is handled in Post#clean_fav_string!
-    post.score += 1 if user.is_gold?
+    Favorite.transaction do
+      return if Favorite.for_user(user.id).where(:user_id => user.id, :post_id => post.id).exists?
+      Favorite.create(:user_id => user.id, :post_id => post.id)
+      Post.update_all("fav_count = fav_count + 1", {:id => post.id})
+      Post.update_all("score = score + 1", {:id => post.id}) if user.is_gold?
+      post.append_user_to_fav_string(user.id)
+      User.update_all("favorite_count = favorite_count + 1", {:id => user.id})
+      user.favorite_count += 1
+      # post.fav_count += 1 # this is handled in Post#clean_fav_string!
+      post.score += 1 if user.is_gold?
+    end
   end
 
   def self.remove(post, user)
-    return unless Favorite.for_user(user.id).where(:user_id => user.id, :post_id => post.id).exists?
-    Favorite.destroy_all(:user_id => user.id, :post_id => post.id)
-    Post.update_all("fav_count = fav_count - 1", {:id => post.id})
-    Post.update_all("score = score - 1", {:id => post.id}) if user.is_gold?
-    post.delete_user_from_fav_string(user.id)
-    User.update_all("favorite_count = favorite_count - 1", {:id => user.id})
-    user.favorite_count -= 1
-    post.fav_count -= 1
-    post.score -= 1 if user.is_gold?
+    Favorite.transaction do
+      return unless Favorite.for_user(user.id).where(:user_id => user.id, :post_id => post.id).exists?
+      Favorite.destroy_all(:user_id => user.id, :post_id => post.id)
+      Post.update_all("fav_count = fav_count - 1", {:id => post.id})
+      Post.update_all("score = score - 1", {:id => post.id}) if user.is_gold?
+      post.delete_user_from_fav_string(user.id)
+      User.update_all("favorite_count = favorite_count - 1", {:id => user.id})
+      user.favorite_count -= 1
+      post.fav_count -= 1
+      post.score -= 1 if user.is_gold?
+    end
   end
 end