OStruct-like that raises raises error on non-existent keys.

ohash.rb

class OHash < Hash
  def initialize(key_values)
    key_values.each { |key, value| self[key] = value }
  end

  def method_missing(key)
    if self.has_key?(key)
      return self[key]
    else
      raise NoMethodError
    end
  end
end

struct = OHash.new(:a => 1, :b => 2)
struct.a # => 1
struct.b # => 2
struct.c # => NoMethodError