Create a local key value store using only the standard library in ruby

example.rb

require 'localstore'

DB.set(key: "value")
DB.exists?(:key) # => true
DB.get(:key) # => "value"
DB.get(:other, "default value") # => default val
DB.get(:other) do
  val = computed_val()
  DB.set(other: val)
  val
end
# => value of val in block
DB.keys # => [:key, :other]
DB.del(:key)
DB.clear()

localstore.rb

require "pstore"
require "forwardable"

class DB
  extend SingleForwardable
  def_delegators :new, :keys, :exists?, :set, :get, :del, :clear

  attr_reader :db

  def initialize(path: ".db.pstore")
    @db = PStore.new(path)
  end

  def keys
    db.transaction(true) { db.roots }
  end

  def exists?(key)
    db.transaction(true) { db.root?(key) }
  end

  def set(**args)
    db.transaction do
      args.each {|key, val| val.nil? ? db.delete(key) : db[key] = val}
    end
  end

  def get(key, default=nil)
    val = db.transaction(true) { db[key] }
    return val unless val.nil?
    return default unless default.nil?
    return yield if block_given?
    nil
  end

  def del(*args)
    db.transaction { args.each { |key| db.delete(key) } }
  end

  def clear
    del(*keys)
  end
end