how to change values between tags in a string

If I have the开发者_JAVA百科 following string:

str="hello %%one_boy%%'s something %%four_girl%%'s something more"

how would I edit it to get the following output from printing str:

"hello ONE_BOY's something FOUR_GIRL's something more"

I have been trying to use 'gsub' and 'upcase' methods but am struggling with the regex to get each word between my '%%' symbols.

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ruby-1.9.2-p136 :066 > str.gsub(/%%([^%]+)%%/) {|m| $1.upcase}
 => "hello ONE_BOY's something FOUR_GIRL's something more" 

The [^%]+ says it will match 1 or more characters except %, and the $1is a global variable that stores the back reference to what was matched.

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s.gsub(/%%([^%]+)%%/) { $1.upcase }

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Here's a quick and dirty way:

"hello %%one_boy%%'s something %%four_girl%%'s something more".gsub(/(%%.*?%%)/) do |x|
    x[2 .. (x.length-3)].upcase
end

The x[2 .. (x.length-3)] bit slices out the middle of the match (i.e. strips off the leading and trailing two characters).

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If you're able to choose the delimiters, you might be able to use String.interpolate from the Facets gem:

one_boy = "hello".upcase
str = "\#{one_boy}!!!"
String.interpolate{ str }    #=> "HELLO!!!"

But I'd first check that Facets doesn't cause any conflicts with Rails.

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str.gsub(/%%([^%]+)%%/) { |match| $1.upcase }