Try pluck, fallback to select and collect

Author: sturgill

lib/closure_tree/acts_as_tree.rb

@@ -352,7 +352,7 @@ def without_self(scope)
     end
 
     def ids_from(scope)
-      scope.uniq.pluck(:id)
+      scope.try(:pluck, :id) || scope.select(:id).collect(&:id)
     end