Simple Loading iOS - Objective C

UIActivityIndicatorView *spinner;
//-------------
spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    spinner.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray;
    [spinner setCenter:CGPointMake([UIScreen mainScreen].bounds.size.width / 2.0, [UIScreen mainScreen].bounds.size.height/2.0)];
    [self.view addSubview:spinner];
//--------------
 [spinner startAnimating];
//--------------
[spinner stopAnimating];