Date based version number generator for fast lane (YYYYMMDD.0)

fastfile.rb

platform :ios do
  lane :beta do
    # ...
    increment_build_number(xcodeproj: "ProjectName.xcodeproj",
                            build_number: date_based_build_number)
  end

  # Generate todays date formatted for version
  def today_formatted
    Date.today.strftime('%Y%m%d')
  end

  # Generate build number with format: YYYMMDD.0    automatically increments 0 if same day
  def date_based_build_number
    current_build_number = get_build_number(xcodeproj: "FitMatch.xcodeproj")

    build_number_parts = current_build_number.split(".")

    build_date = build_number_parts[0]
    build_version = build_number_parts[1]

    if (!build_date || !build_version) || (build_date.empty? || build_version.empty?)
      return default_build_number
    end

    begin
      build_date_object = Date.strptime(build_date, '%Y%m%d')
    rescue
      return default_build_number
    end

    if build_date_object.today?
      new_version = build_version.to_i + 1
      return "#{today_formatted}.#{new_version}"
    end

    return default_build_number
  end
  
  # Default build number to avoid replicating code
  def default_build_number
    "#{today_formatted}.0"
  end
end