When using in-app audio in the iPhone SDK, it is possible to allow users to select a list from their ipod library and create an in-app local playlist. If I want to persist this choice, it is easy to serialize the data and write to file, then recover.
Just vanilla like this, however, leads me to think there is going to be something wrong. For example, what if the user syncs and removes sounds? I can loop across them all and query the iPod DB at setup time, but with lists that could be 50,000 long, this could take some time.
How are other people doing this and what are some gotchas that I haven't though about?