title: Which local folder does ios dropbox to save?
body: <p>I want to know, how to save file to local storage. Like dropbox for iOS and many other similar app. 
  I read the Apple Document, we can save file to cache and tmp, I want to save to local storage for ever, so the files in cache and tmp folder will be removed by system.
  How does dropbox to save in the local storage?</p>
  
  <p>I want to develop a app, encrypt file, then save to local.  We can not save to Document, because apple will reject.</p>
  
  <p>I have no idear, where to save.</p>