Nano ID for Ruby

concern.rb

module PublicID
  # https://planetscale.com/blog/why-we-chose-nanoids-for-planetscales-api
  extend ActiveSupport::Concern

  included do
    before_create :set_pid
  end

  PUBLIC_ID_MAX_RETRIES = 1000

  private

  def set_pid
    return if pid.present?
    PUBLIC_ID_MAX_RETRIES.times do
      self.pid = NanoID.generate
      return unless self.class.exists?(pid: pid)
    end
    raise "Failed to generate a unique pid"
  end
end

nano_id.rb

module NanoID
  # https://github.com/ai/nanoid/blob/main/index.js
  extend self

  URL_ALPHABET = "useandom-26T198340PX75pxJACKVERYMINDBUSHWOLF_GQZbfghjklqvwyzrict"

  def generate(size = 21)
    bytes = SecureRandom.bytes(size).bytes
    id = +""
    bytes.each { |c| id << URL_ALPHABET[c & 63] }
    id
  end
end