Converting upper-case string into title-case using Ruby

Question

I\'m trying to convert an all-uppercase string in Ruby into a lower case one, but with each word\'s first character being upper case. Example:

convert \"MY STRING HE

Answer 1

I've try to improve code... ready for critics and suggestions.

class Book
    attr_accessor :title
    def title=(new_title)
    notcap=%w(and the a in of an)
    str=''
    new_title.gsub(/(\w|\s)\w+/) do |word|
        word.strip!
        if not notcap.include? word
               word.capitalize! 
        end
       str += ' ' + word 
    end
    str.strip!
    str = str[0].upcase + str[1..-1]
    @title = str
   end
end