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, 5 insertions, 5 deletions

diff --git a/lib/axlsx/workbook/worksheet/data_validation.rb b/lib/axlsx/workbook/worksheet/data_validation.rb
index 1b9cb46a..d5fa5908 100644
--- a/lib/axlsx/workbook/worksheet/data_validation.rb
+++ b/lib/axlsx/workbook/worksheet/data_validation.rb
@@ -237,12 +237,12 @@ module Axlsx
       valid_attributes = get_valid_attributes
 
       str << '<dataValidation '
-      str << Axlsx.instance_values_for(self).map do |key, value|
-        +'' << key << '="' << Axlsx.booleanize(value).to_s << '"' if (valid_attributes.include?(key.to_sym) && !CHILD_ELEMENTS.include?(key.to_sym))
-      end.join(' ')
+      Axlsx.instance_values_for(self).each do |key, value|
+        str << key << '="' << Axlsx.booleanize(value).to_s << '" ' if (valid_attributes.include?(key.to_sym) && !CHILD_ELEMENTS.include?(key.to_sym))
+      end
       str << '>'
-      str << (+'<formula1>' << self.formula1 << '</formula1>') if @formula1 and valid_attributes.include?(:formula1)
-      str << (+'<formula2>' << self.formula2 << '</formula2>') if @formula2 and valid_attributes.include?(:formula2)
+      str << '<formula1>' << self.formula1 << '</formula1>' if @formula1 and valid_attributes.include?(:formula1)
+      str << '<formula2>' << self.formula2 << '</formula2>' if @formula2 and valid_attributes.include?(:formula2)
       str << '</dataValidation>'
     end