initializer_struct.rb

class InitializerStruct
  def self.new(*args)
    Class.new do
      define_method(:initialize) do |*initializer_args|
        arity_error = ArgumentError.new("wrong number of arguments (#{initializer_args.size} for #{args.size})")
        raise arity_error unless initializer_args.size == args.size

        args.each do |arg|
          instance_variable_set("@#{arg}", initializer_args.shift)
        end
      end
    end
  end
end

class Dummy < InitializerStruct.new(:a, :b)
end

puts Dummy.new(1, 2).inspect
puts Dummy.new(1).inspect