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

NSUserDefaults is basically a wrapper for loading a NSDictionary from a .plist file from the disk (and also writing it to the disk). You can store as much data in NSUserDefaults, but you have little control over how much memory it uses, and how it reads from the disk.

I would use different technologies for different information/data.

• Small bits of data from servers, preferences, user info, et cetera, I would use NSUserDefaults.

• For login information (access tokens, sensitive data), I would use the keychain. The keychain could also be used for data that should not be deleted when the app is deleted.

• For large amounts of server data or game data, I would write it to the disk, but keep it in memory.

In your situation, I would keep it in memory (probably a @property), but I would periodically write it to the disk (perhaps every 1 to 5 times it changes, use an int ivar). Make sure that this disk writing method is in the AppDelegate, so that it won't fail when you close the view controller that is executing it.

This way, the data is easily accessed, but its also saved to the disk for safe keeping.