Pipe output directly to str and avoid additional memory allocations

Currently, there are lots of examples of code like this,
```
str << ('<tag ' << foo << ' ' << bar << '/>')
```
which create the string for the tag in memory before piping to str.

We can avoid creating all of these intermediate strings by dropping
the paranthesis and piping directly to str.

This relies on the `str` passed around to handle lots of small
appends. This is a problem when using RubyZip, but that is solved
in the next commit.

1 files changed, 10 insertions, 10 deletions

diff --git a/lib/axlsx/workbook/worksheet/pivot_table.rb b/lib/axlsx/workbook/worksheet/pivot_table.rb
index e97b8119..27065e4b 100644
--- a/lib/axlsx/workbook/worksheet/pivot_table.rb
+++ b/lib/axlsx/workbook/worksheet/pivot_table.rb
@@ -189,10 +189,10 @@ module Axlsx
     def to_xml_string(str = +'')
       str << '<?xml version="1.0" encoding="UTF-8"?>'
 
-      str << (+'<pivotTableDefinition xmlns="' << XML_NS << '" name="' << name << '" cacheId="' << cache_definition.cache_id.to_s << '"' << (data.size <= 1 ? ' dataOnRows="1"' : '') << ' applyNumberFormats="0" applyBorderFormats="0" applyFontFormats="0" applyPatternFormats="0" applyAlignmentFormats="0" applyWidthHeightFormats="1" dataCaption="Data" showMultipleLabel="0" showMemberPropertyTips="0" useAutoFormatting="1" indent="0" compact="0" compactData="0" gridDropZones="1" multipleFieldFilters="0">')
+      str << '<pivotTableDefinition xmlns="' << XML_NS << '" name="' << name << '" cacheId="' << cache_definition.cache_id.to_s << '"' << (data.size <= 1 ? ' dataOnRows="1"' : '') << ' applyNumberFormats="0" applyBorderFormats="0" applyFontFormats="0" applyPatternFormats="0" applyAlignmentFormats="0" applyWidthHeightFormats="1" dataCaption="Data" showMultipleLabel="0" showMemberPropertyTips="0" useAutoFormatting="1" indent="0" compact="0" compactData="0" gridDropZones="1" multipleFieldFilters="0">'
 
-      str << (+'<location firstDataCol="1" firstDataRow="1" firstHeaderRow="1" ref="' << ref << '"/>')
-      str << (+'<pivotFields count="' << header_cells_count.to_s << '">')
+      str << '<location firstDataCol="1" firstDataRow="1" firstHeaderRow="1" ref="' << ref << '"/>'
+      str << '<pivotFields count="' << header_cells_count.to_s << '">'
 
       header_cell_values.each do |cell_value|
         subtotal = !no_subtotals_on_headers.include?(cell_value)
@@ -205,12 +205,12 @@ module Axlsx
         str << '<rowFields count="1"><field x="-2"/></rowFields>'
         str << '<rowItems count="2"><i><x/></i> <i i="1"><x v="1"/></i></rowItems>'
       else
-        str << (+'<rowFields count="' << rows.size.to_s << '">')
+        str << '<rowFields count="' << rows.size.to_s << '">'
         rows.each do |row_value|
-          str << (+'<field x="' << header_index_of(row_value).to_s << '"/>')
+          str << '<field x="' << header_index_of(row_value).to_s << '"/>'
         end
         str << '</rowFields>'
-        str << (+'<rowItems count="' << rows.size.to_s << '">')
+        str << '<rowItems count="' << rows.size.to_s << '">'
         rows.size.times do |i|
           str << '<i/>'
         end
@@ -229,16 +229,16 @@ module Axlsx
           str << '<colItems count="1"><i/></colItems>'
         end
       else
-        str << (+'<colFields count="' << columns.size.to_s << '">')
+        str << '<colFields count="' << columns.size.to_s << '">'
         columns.each do |column_value|
-          str << (+'<field x="' << header_index_of(column_value).to_s << '"/>')
+          str << '<field x="' << header_index_of(column_value).to_s << '"/>'
         end
         str << '</colFields>'
       end
       unless pages.empty?
-        str << (+'<pageFields count="' << pages.size.to_s << '">')
+        str << '<pageFields count="' << pages.size.to_s << '">'
         pages.each do |page_value|
-          str << (+'<pageField fld="' << header_index_of(page_value).to_s << '"/>')
+          str << '<pageField fld="' << header_index_of(page_value).to_s << '"/>'
         end
         str << '</pageFields>'
       end