NSUserDefaults physically data

Question

I'm wondering if there's anywhere i can see what data is in my NSUserDefaults? Like, how does it works? Is there a file that stores in my iphone that contains all the data in the NSUserDefaults or is the file stores in different apps? If i have set [NSUserDefaults standardUserDefaults] setObject:someString forKey:@"someString"]; in app A, can i use NSString *listData = [[NSUserDefaults standardUserDefaults] stringForKey:@"someString"] to get the string in another app B? Is there somewhere the NSUserDefaults is physically stored?

Answer 1

The preferences of your app are stored in a .plist file (in binary format) in [APP_BASE_DIR]/Library/Preferences/.

See ~/Library/Application Support/iPhone Simulator/4.1/Applications to see the app base dirs in the iPhone Simulator.

Answer 2

The NSUserDefaults is stored in a plist file; on the iPhone and iPad, you cannot simply open these files. However, you can have your app print out the contents to the debugger.

Answer 3

I believe sandboxing will prevent accessing another application's user defaults under iOS. Under Mac OS X, you can work with another application's user defaults by dropping down to the CFPreferences API:

/* ownership follows the Create/Copy rule, so must release when done -
 * here, I just autorelease */
NSString *
value = [(id)CFPreferencesCopyAppValue(CFSTR("key"), CFSTR("com.foo.otherapp"))
         autorelease];
if ([value isKindOfClass:[NSString class]]) {
    /* use the string */
}