When (not) to abuse NSUserDefaults

Question

I wonder what the guidelines are for:
1 - how often I can read from NSUserDefaults
2 - how much data I can reasonably store in NSUserDefaults

Obviously, ther

Answer 1

Don't worry about limits. Instead, ask yourself this simple question:

Is this a preference?

If it is a preference, then it should be in user defaults. That's what user defaults is for. If not, then it should be in the Documents directory (or, on the Mac, possibly in Application Support).

On iOS, you might tell whether it's a preference or not by whether it would be appropriate to (if possible) put it in your settings bundle for display and editing in the Settings application. On Mac OS X, you can usually tell whether it's a preference or not by whether it would be appropriate to put it in the Preferences window.

Of course, that relies on your judgment. Stanza for Mac, for example, gets it wrong, putting non-preferences in its Preferences window.

You can also consider the question by its converse:

Is this user-created data?

A preference that you will have a default value for is not user-created data; it is user-overridden data. No less bad to lose it, but it informs where you should keep it.