把标准数据结构转换成扁平数据形式，可被保存到磁盘或通过网络传输，供以后重新构造数据结构

class Person
attr_accessor :name
end
fred = Person.new
fred.name = 'Fred Bloggs'
laura = Person.new
laura.name = 'Laura Smith'

require 'pstore'
store = PStore.new('storagefile')
store.transaction do
store[:people] ||= Array.new
store[:people] << fred
store[:people]<<laura
end

#以后就可以从PStore数据库中检索数据

require 'pstore'
store = PStore.new('storagefile')
people = []
store.transaction do 
people = store[:people]
end

people.each do |p|
puts p.name
end