Null Object Pattern

active_nothing.rb

# Active Nothing - Null Object Pattern
class Bot
  FAUX_DATABASE = [{ id: 1, name: 'KITT' }, { id: 3, name: 'GERTY' }].freeze

  attr_reader :name

  def self.find(id)
    row = FAUX_DATABASE.find{ |r| r[:id] == id }
    return nil if row.nil?
    new(row)
  end

  def initialize(row)
    @name = row.dig(:name)
  end
end

class MissingBot
  def name
    'missing robot'
  end
end

# wrap both in another class
class GuaranteedRobot
  def self.find(id)
    Bot.find(id) || MissingBot.new
  end
end

# if there is no Bot in the db, we will return an
# instance of our MissingBot which responds to `#name`
bots = [1,2,3].map { |id| GuaranteedRobot.find(id).name }
puts bots