Unexpected results from NSUserDefaults boolForKey

After uninstalling an application completely from the device and then loading it in the debugger, I am attempting in a setup method to load a flag using boolForKey. The first time the app runs I have the expectation that the bool will not exist, since I have just reinstalled the app. I expect from the documentation that boolForKey will therefore return NO.

I am seeing the opposite th开发者_如何学JAVAough. boolForKey is returning YES, which fubars my initial user settings. Any idea why this might be happening or a good way around it?

BOOL stopAutoLogin = [[NSUserDefaults standardUserDefaults] boolForKey:@"StopAutoLogin"];
_userWantsAutoLogin = !stopAutoLogin;

So stopAutoLogin comes out as "YES", which is completely unexpected.

Stranger and stranger: When I call objectForKey:@"StopAutoLogin" I get a nil object, as expected. It's just the boolForKey that returns a bad value. So I changed the code to this:

// this is nil
NSObject *wrapper = [[NSUserDefaults standardUserDefaults] objectForKey:@"StopAutoLogin"];

// this is YES
BOOL stopAutoLogin = [[NSUserDefaults standardUserDefaults] boolForKey:@"StopAutoLogin"];

please try [UserDefaults synchronize];

Because this method is automatically invoked at periodic intervals, use this method only if you cannot wait for the automatic synchronization (for example, if your application is about to exit) or if you want to update the user defaults to what is on disk even though you have not made any changes.

please see: http://developer.apple.com/library/ios/#documentation/Cocoa/Reference/Foundation/Classes/NSUserDefaults_Class/Reference/Reference.html

Do you register the default values for your keys?

NSMutableDictionary *appDefaults = [NSMutableDictionary dictionaryWithCapacity:1];
[appDefaults setObject:@"NO" forKey:kReloadOnStartKey];
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults registerDefaults:appDefaults];

If there is no registration domain, one is created using the specified dictionary, and NSRegistrationDomain is added to the end of the search list.

The contents of the registration domain are not written to disk; you need to call this method each time your application starts. You can place a plist file in the application's Resources directory and call registerDefaults: with the contents that you read in from that file.

See this link for more information.