NSUserDefaults not writing to disk - objective-c

Question

I have a small background Mac (menubar) app which uses preferences for one simple value (string). When I launch the app from Xcode, it will almost always report the pref as being set, even when the plist does not exist in ~/Library/Preferences. Without making any codebase changes, it appears to occassionally write the prefs file upon subsequent launches. It does have a helper app which runs normally, and a Today extension, if it matters. I've tried using the [defaults synchronize] command, it doesn't do anything. I have other apps which work fine. I don't access or set NSUSerDefaults (including bindings) anywhere else in my project
Currently, my app is NOT sandboxed.
some sample code:
NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];
[standardDefaults synchronize];
NSLog(#"value for key is %#", [standardDefaults valueForKey:#"firstTime"]);
//this always reports back as "Accepted" even when no pref exists
if ([[standardDefaults valueForKey:#"first"] isEqualToString:#"Accepted"])
{
NSLog(#"accepted");
//always seen
}
else
{
//rarely seen except in complete random times
NSLog(#"first time");
#try
{
NSLog(#"alert");
[standardDefaults setObject:#"Accepted" forKey:#"first"];
[standardDefaults synchronize];
}
#catch (NSException *exception)
{
NSLog(#"exception is %#", exception);
}
#finally
{
}
}
UDPATE: I now see this on new apps, non-sandboxed. Bizarre. I created a brand-new mac/Cocoa app, and used this code:
- (void)viewDidLoad
{
[super viewDidLoad];
NSUserDefaults *standardDefaults = [NSUserDefaults standardUserDefaults];
[standardDefaults synchronize];
NSLog(#"value for key is %#", [standardDefaults valueForKey:#"firstTime"]);
if (![standardDefaults valueForKey:#"firstTime"])
{
NSLog(#"settings value for key");
[standardDefaults setValue:#"Whatever" forKey:#"firstTime"];
[standardDefaults synchronize];
}
NSLog(#"value for key is %#", [standardDefaults valueForKey:#"firstTime"]);
// Do any additional setup after loading the view.
}
The first time, it reports as missing. Every attempt afterwards, tt immediately registers as the pref existing and reporting as "whatever", even when the pref file is most definitely not there.

Answer 1

The file is normally periodically written by cfprefsd. All times you read/write the values you're actually talking to cfprefsd, not to the file on disk.
When you synchronize, it causes cfprefsd to get the values that you've set, again, not guaranteeing that it is written to disk.
The condition you've stated seems to indicate that the preference was set the first time round, and even though you've not seen the file appear on disk, it's reading the values. This is the expected behaviour.
If you want to test resetting the preferences before writing, you need to clear them out, using something like:
NSString *appDomain = [[NSBundle mainBundle] bundleIdentifier];
[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];
I believe that since the introduction of cloud preference syncing, it's become a more noticeable issue that the file doesn't appear. Modifying the file has never been considered stable.
If you want to delete the preferences from the command line, you should use defaults delete (I don't have a mac at hand to give you the exact command line for this, though).