Convert php-style nested attribute arrays to rails-style. Dirty hack.

convert_restkit_params.rb

# put this into config/initializers

module Rack
  module Utils
    def parse_nested_query_with_restkit(qs, d = nil)
      qs = RestkitConverter.new.convert(qs) if qs[/\[\]/]
      parse_nested_query_without_restkit(qs, d)
    end
    alias_method_chain :parse_nested_query, :restkit
    module_function :parse_nested_query
    module_function :parse_nested_query_without_restkit
  end
end

class RestkitConverter
  def convert(s)
    transform_lines(s.split('&')).join('&')
  end

  protected

  def transform_lines(lines)
    grouped_lines = lines.group_by { |line| line[/.*?\[\]/] || '' }

    return lines if grouped_lines.length == 1

    grouped_lines.map { |prefix, sublines|
      sublines = sublines.map { |line| line[prefix.length..-1] }

      key = sublines.first[/[^=]*/]
      groups = sublines.inject([]) { |accum, line|
        accum << [] if line[/[^=]*/] == key
        accum.last << line
        accum
      }

      groups.map_with_index { |group, i|
        transform_lines(group).map { |line|
          prefix.gsub(/\[\]/, "[#{i}]") + line
        }
      }
    }.flatten
  end
end

module Enumerable
  def map_with_index
    result = []
    self.each_with_index do |elt, idx|
      result << yield(elt, idx)
    end
    result
  end
end