NSUserDefault无法检索到双精度值

Question

I'm creating a simple double value, saving it as NSUserDefault and trying to recover it...but it doesn't.

- (IBAction)try:(id)sender {

    double value = 42.00;

    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    [defaults setDouble:value forKey:@"kDoubleKey"];
   // NSLog(@"loading %f",myDouble);
}


-(void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];

    NSUserDefaults *fetchDefaults = [NSUserDefaults standardUserDefaults];
    double intValue = [fetchDefaults doubleForKey:@"kDoubleKey"];
    NSLog(@"douvle retrieve %f",intValue);
}

Answer 1

Do not forget to synchronise whenever you save something to the defaults: put this at the end of your try method

[[NSUserDefaults standardUserDefaults]synchronize];

Here is what apple says about this: 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.