class OpenStruct

def initialize(hash=nil)
  @table = {}
  if hash
    hash.each_pair do |k, v|
      k = k.to_sym
      @table[k] = v
      new_ostruct_member(k)
    end
  end
end

def method_missing(mid, *args) # :nodoc:
  mname = mid.id2name
  len = args.length
  if mname.chomp!('=')
    if len != 1
      raise ArgumentError, "wrong number of arguments (#{len} for 1)", caller(1)
    end
    modifiable[new_ostruct_member(mname)] = args[0]
  elsif len == 0
    @table[mid]
  else
    err = NoMethodError.new "undefined method `#{mid}' for #{self}", mid, args
    err.set_backtrace caller(1)
    raise err
  end
end

def modifiable
  begin
    @modifiable = true
  rescue
    raise RuntimeError, "can't modify frozen #{self.class}", caller(3)
  end
  @table
end

def new_ostruct_member(name)
  name = name.to_sym
  unless respond_to?(name)
    define_singleton_method(name) { @table[name] }
    define_singleton_method("#{name}=") { |x| modifiable[name] = x }
  end
  name
end