One way to use classes to facilitate cleaner interactions with Redis as the main "database"

clean-redis-playlist.rb

class Playlist
  def initialize(playlist={})
    return nil unless playlist["tracks"] and playlist["author"]

    num = $redis.incr("playlists:num")
    next_id = $redis.incr("playlists:next_id")
    $redis.sadd("playlists:all", next_id)

    playlist["date"] = Time.now
    playlist["id"] = next_id

    playlist.each_pair do |key, val|
      $redis.hset("playlists:#{next_id}", key, val)
    end

    if playlist["name"]
      $redis.set("playlists:by_name:#{playlist["name"].gsub(/\W/, "_")}", next_id)
    end

    return playlist
  end

  def self.get_all
    playlists = []
    $redis.smembers("playlists:all").each do |n|
      playlists << self.get_by_id(n)
    end

    return playlists
  end

  def self.get_by_id(id)
    playlist = $redis.hgetall("playlists:#{id}")
    playlist['tracks'] = $redis.smembers("tracks:#{playlist['tracks']}")
    return playlist
  end

  def self.get_by_name(name)
    track_id = $redis.get("playlists:by_name:#{name.gsub(/\W/, "_")}")
    return self.get_by_id(track_id)
  end

  def self.delete_by_id(id)
    $redis.srem("playlists:all", id)
    $redis.hdel("playlists:#{id}")
    $redis.decr("playlists:num")
  end

  def self.delete_by_name(name)
    id = $redis.get("playlists:by_name:#{name}")
    $redis.del("playlists:by_name:#{name}")
    self.delete_by_id(id)
  end
end