Easier helper for filtering secured categories

app/models/group.rb

@@ -46,15 +46,7 @@ class Group < ActiveRecord::Base
                  .where('topics.archetype <> ?', Archetype.private_message)
                  .where(post_type: Post.types[:regular])
 
-    unless guardian.is_admin?
-      allowed_ids = guardian.allowed_category_ids
-      if allowed_ids.length > 0
-        result = result.where('topics.category_id IS NULL or topics.category_id IN (?)', allowed_ids)
-      else
-        result = result.where('topics.category_id IS NULL')
-      end
-    end
-
+    result = guardian.filter_allowed_categories(result)
     result = result.where('posts.id < ?', before_post_id) if before_post_id
     result.order('posts.created_at desc')
   end

lib/guardian/topic_guardian.rb

@@ -67,6 +67,19 @@ module TopicGuardian
 
     # not secure, or I can see it
     !topic.read_restricted_category? || can_see_category?(topic.category)
+  end
+
+  def filter_allowed_categories(records)
+    unless is_admin?
+      allowed_ids = allowed_category_ids
+      if allowed_ids.length > 0
+        records = records.where('topics.category_id IS NULL or topics.category_id IN (?)', allowed_ids)
+      else
+        records = records.where('topics.category_id IS NULL')
+      end
+      records = records.references(:categories)
+    end
+    records
+  end
 
 end
-end

lib/topic_query.rb

@@ -359,18 +359,7 @@ class TopicQuery
       result = result.where('topics.posts_count <= ?', options[:max_posts]) if options[:max_posts].present?
       result = result.where('topics.posts_count >= ?', options[:min_posts]) if options[:min_posts].present?
 
-      guardian = Guardian.new(@user)
-      if !guardian.is_admin?
-        allowed_ids = guardian.allowed_category_ids
-        if allowed_ids.length > 0
-          result = result.where('topics.category_id IS NULL or topics.category_id IN (?)', allowed_ids)
-        else
-          result = result.where('topics.category_id IS NULL')
-        end
-        result = result.references(:categories)
-      end
-
-      result
+      Guardian.new(@user).filter_allowed_categories(result)
     end
 
     def remove_muted_categories(list, user, opts=nil)

spec/components/guardian_spec.rb

@@ -19,7 +19,7 @@ describe Guardian do
     expect { Guardian.new }.not_to raise_error
   end
 
-  it 'can be instantiaed with a user instance' do
+  it 'can be instantiated with a user instance' do
     expect { Guardian.new(user) }.not_to raise_error
   end