Version helper class

version.rb

class Version
  include Comparable

  PATTERN = /^(?<major>0|[1-9][0-9]*)(\.(?<minor>0|[1-9][0-9]*))?(\.(?<revision>0|[1-9][0-9]*))?$/
  
  attr_reader :major, :minor, :revision

  def initialize(options)
    [:major, :minor, :revision].each do |field|
      validate_field(field, options[field])
      instance_variable_set("@#{field}", options[field] || 0)
    end
  end

  def self.parse(string, options = {})
    match = PATTERN.match(string)
    return nil unless match

    Version[match[:major], match[:minor], match[:revision]]
  end

  def self.[](*array)
    new(major: array[0].to_i, 
        minor: array[1].to_i,
        revision: array[2].to_i)
  end

  def self.parse!(string, options = {})
    parse(string) || (raise ArgumentError, "invalid version format")
  end

  def <=>(other_version)
    comparison = 0
    [:major, :minor, :revision].each do |field|
      comparison = self.send(field) <=> other_version.send(field)
      break if comparison != 0
    end

    comparison
  end

  def to_s
    @as_string ||= [major, minor, revision].join('.')
  end

  private
    def validate_field(field, value)
      if value
        raise ArgumentError, "#{field} field must be an integer" unless value.is_a?(Integer)
      end
    end
end