NSKeyedArchiver working on simulator but not actual device

Question

I cannot seem to get NSKeyedArchiver working. I have a main ViewController, which has an NSMutableArray as an instance variable. The array is populated by multiple instances of a custom class. The custom class conforms to the NSCoding protocol and implements both the encoding and decoding methods. From the main view controller, I call

- (NSString *)itemArchivePath
{
NSArray *documentDirectories = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

//only one document in list - get path t o it
NSString *documentDirectory = [documentDirectories firstObject];

return [documentDirectory stringByAppendingString:@"locations.archive"];
}

- (BOOL)saveChanges
{
//returns success or failure
NSString *path = [self itemArchivePath];

return [NSKeyedArchiver archiveRootObject:myArray //this is the array to archive
                                   toFile:path];
}

In the app delegate, I call the saveChanges method for applicationDidEnterBackground. The method returns true on the simulator, but false for the actual device. I am not sure what to do. Any help is appreciated. Thanks!

EDIT: Based on Zaph's comment, I have changed the saveChanges method to:

- (void)saveChanges
{
//returns success or failure
NSString *path = [self itemArchivePath];

NSData *dataOfArray = [NSKeyedArchiver archivedDataWithRootObject:myArray];
NSFileManager *checker = [NSFileManager defaultManager];
[dataOfArray writeToFile:path
              atomically:YES];

if ([checker fileExistsAtPath:path]) {
    NSLog(@"Archive Successful");

}
else {
    NSLog(@"Archive Did Not Work");
}

}

Answer 1

NSLog the path! It is probably wrong as @Wolfgang states.

[documentDirectory stringByAppendingString:@"locations.archive"]

will not add a "/" between the path and filename. use:

[documentDirectory stringByAppendingPathComponent:@"locations.archive"]

When code does not work make it as simple as possible, break up compound statements into individual statements. Then follow along with the debugger and/or NSLog() statements checking every step.