Second max number

second_max_number..rb

def second_max_number(array)
  raise 'Argument array must be an enumerable' unless array.is_a?(Enumerable)
  raise 'Argument array must have at least 2 elements' if array.size < 2

  max, second_max = nil
  array.each do |current|
    if max.nil? || (!current.nil? && current > max)
      if second_max.nil? || (!max.nil? && max > second_max)
        second_max = max
      end
      max = current
    elsif second_max.nil? || (!current.nil? && current > second_max)
      second_max = current
    end
  end
  second_max
end