+ # Check that any fields in @select are valid for at least one class
+ if @select
+ all_attributes = []
+ klasses.each do |klass|
+ all_attributes.concat klass.selectable_attributes
+ end
+ @select.each do |check|
+ if !all_attributes.include? check
+ raise ArgumentError.new "Invalid attribute '#{check}' in select"
+ end
+ end
+ end
+ any_selections = @select
+