ruby 下的 strip_html

類似 php 下的 strip_tags , 可提供 allow_tag !!

   def self.strip_html(str, allow = ['a','img','p','br','i','b','u','ul','li'])
      str.strip!
      allow_arr = allow.join('\\b|') << '|/'
      tag_pat = %r,<(?:(?:/?)|(?:\s*))(?!#{allow_arr}).*?>,
      str.gsub(tag_pat, ' ')
  end

http://www.bigbold.com/snippets/posts/show/535