Implementing Struct (solution to https://gist.github.com/JoshCheek/2641441)

my_struct.rb

# solution to https://gist.github.com/JoshCheek/2641441
class MyStruct
  def self.new(*members, &block)
    members.none? and raise ArgumentError, 'wrong number of arguments (must provide at least one)'
    members.each { raise TypeError, "Expected a Symbol, got #{_1.inspect}" unless _1.is_a? Symbol }

    Class.new Instance do
      @members = members
      members.each do |name|
        define_method(name) { self[name] }
        define_method("#{name}=") { |value| self[name] = value }
      end
      class_eval &block if block
    end
  end

  class Instance
    def self.members
      @members.dup
    end

    def initialize(*params)
      @attributes = self.class.members.zip(params).to_h { [_1, _2] }
    end

    def [](key)
      key = normalize_key key
      @attributes.fetch(key) { raise NameError, "no member '#{key}' in struct" }
    end

    def []=(key, value)
      @attributes[normalize_key key] = value
    end

    def inspect
      "#<struct #{@attributes.map { %'#{_1}=#{_2.inspect}' }.join(', ')}>"
    end

    def members
      @attributes.keys
    end

    def values
      @attributes.values
    end

    def select(&block)
      values.select(&block)
    end

    def size
      @attributes.size
    end

    include Enumerable

    def each(&block)
      values.each(&block)
    end

    private

    def normalize_key(key)
      if key.respond_to? :to_sym
        key = key.to_sym
        return key if @attributes.key? key
        raise NameError, "no member '#{key}' in struct"
      end

      if key.respond_to? :to_int
        return members.fetch key.to_int do
          raise IndexError, "offset #{key} too large for struct(size:#{size})"
        end
      end

      raise TypeError, "no implicit conversion of #{key.class} into Integer"
    end
  end
end