Ruby's Struct subclass with splats support

splat_struct.rb

#= SplatStruct
# `Struct` subclass with splats support
# 
#     SampleClass = SplatStruct.new(:a, :b, [:c]) do |klass|
#       def avgc
#         Rational(c.inject(:+), c.length).to_f
#       end
#     end
#     
#     object = SampleClass.new(1,2,3,4,5)
#     # => { :a => 1, :b => 2, :c => [3, 4, 5] }

class SplatStruct < Struct
  class << self
    def new(*member_names, &block)
      splat_members = {}
      sstruct_name = member_names[0] if member_names.is_a?(Symbol)
      
      member_names.each.with_index do |member, index|
        next unless member.is_a? Array
        splat_members[member.first] = index - (sstruct_name.nil? ? 0 : 1)
        member_names[index] = member.first
      end
      
      sstruct = super *member_names, &block
      sstruct.instance_variable_set :@_splat_members, splat_members
      sstruct
    end
  end
  
  def self.splat_members
    instance_variable_get :@_splat_members
  end
  
  def initialize(*args)
    self.class.splat_members.values.each {|index| args << args.slice!(index..-1) }
    super *args
  end
end