Ruby Snippets

find_unique.rb

class FindUnique

  DEFAULT_MAX_COMBINATIONS = ((CHARACTERS.size ** UNIQUE_LENGTH) * 0.9)
  TRY_THRESHOLD = 4
  UNIQUE_LENGTH = 6
  CHARACTERS = %w[A B C D E F G H I J K L 1 2 3 4 5 6]

  def self.call
    if Something.count > DEFAULT_MAX_COMBINATIONS
      Rails.logger.warn "This app has used more than 90% of the possible " \
        "combination of external_id's. Adjust FindUnique's constants"
    end

    tries = 0

    loop do
      random_id = generate_random_id

      if tries >= TRY_THRESHOLD
        # Either throw or increase UNIQUE_LENGTH
        throw :unavailable_unique_id
      end

      if !Something.exists?(external_id: external_id)
        something.update_attributes(external_id: external_id)
        break
      end

      tries += 1
    end
  end

  def self.generate_random_id
    letters = []
    while letters.size < UNIQUE_SIZE
      letters << CHARACTERS.sample
    end
    letters.join
  end
  private_class_method :generate_random_id

end