gistfile1.rb

  # Returns a set of hidden fields for params passed in the query string such that they are passed
  # along with the form. Mostly for use with GET forms like search/filtering where you want to retain
  # other state while adding another (<existing params>&q=pr0n)
  #
  # Options:
  #
  #   :skip - An array of keys to leave out - Only works for first-level keys, i.e. not 'bar' in foo[bar]=baz
  def hidden_fields_from_params(opts={})
    #Use CGI.parse to get "raw" parameters that haven't been converted into arrays
    #and hashes yet. This means it only has to concern itself with the one dimension
    #in a query string and not the extra logic added on top with the use of [] and [foo].
    CGI.parse(request.query_string).reject do |key, values|
      opts[:skip].include?(key.gsub(/\[[^\]]*\]/, '')) #Remove [] and [foo] before comparing
    end.map do |key, values|
      values.map{|v| block_given? ? yield(key, v) : hidden_field_tag(key, v) }.join
    end.join.html_safe
  end