lib/axlsx/workbook/worksheet/outline_pr.rb in caxlsx-3.4.1 vs lib/axlsx/workbook/worksheet/outline_pr.rb in caxlsx-4.0.0

@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 module Axlsx
   # The OutlinePr class manages serialization of a worksheet's outlinePr element, which provides various
   # options to control outlining.
   class OutlinePr
     include Axlsx::OptionsParser
@@ -23,10 +25,12 @@
     end
 
     # Serialize the object
     # @param [String] str serialized output will be appended to this object if provided.
     # @return [String]
-    def to_xml_string(str = '')
-      str << "<outlinePr #{serialized_attributes} />"
+    def to_xml_string(str = +'')
+      str << '<outlinePr '
+      serialized_attributes(str)
+      str << '/>'
     end
   end
 end