Property Lists: How to use it to provide easy exchangeable default data to the user?

Question

I want to ship some default data with my app. This data can be stored perfectly in a property list. The strucure is simple:

Root
    0
     animalType = cat
     animalName = Tom
    1
     animalType = dog
     animalName = Rambo

I thought: When I use a property list rather than hard-coding it somewhere, then I could easily provide more defaults to choose from after the app is distributed already. If I would hard-code it, I would have to provide heavy upgrades every time, and Apple would take weeks to let them pass.

But there's one thing I don't get. I make that property list manually in Xcode and put that in my Resources group. As far as I know, Xcode would compile it into some binary format. In my app I would use NSPropertyListSerialization to create a NSDictionary out of it. But this property list would not get placed into the documents directory of the sandbox, right? So if the application would download an update of that property list some time in the future, the update would have to go into documents dir, but the app would still look at the old plist in the root, right? Where to put it? Must I copy it to documents, just like an sqlite database?

And the other thing: When I edit the plist and provide the whole thing as an XML for download/update from a server, then of course that thing would not be "compiled" into some binary format. How would that work? Would NSPropertyListSerialization have trouble reading it? Must I compile that thing every time with XCode and let the app download some binary stuff?

Answer 1

There are two commonly used property list formats: proprientary binary format and xml format (DTD). You can use either of them, and NSPropertyListSerialization will detect automatically, which one is used for your data when de-seralizing.

XML format is more verbose, but it's simple to generate. If you're publishing data from server, you might consider generating xml plist, and compress it with gzip or something.

Now to your first question about where to store the data. To make application payload smaller you might first check documents directory for updated plist, and if it is not present - load default plist from your application bundle.

Answer 2

One general approach used is to always copy plists or other updated elements into the application documents directory - then you just always load from there, and replace when there is an update.

Or you could pre-load the data into a database, download plist updates and refresh the database entries at that time.