Animated replacement of self.navigationItem.rightBarButtonItem with an animated spinner, e.g. when network is busy. Sadly getting the layout right is hard - the width of the rightbarbuttonitem comes back as 0...

gistfile1.m

UIActivityIndicatorView* spinner = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    spinner.hidesWhenStopped = YES;
    [spinner startAnimating];
    
    UIView* view = [[UIView alloc] initWithFrame:CGRectZero];
    view.frame = CGRectMake(0, 0, 20, 30);
    
    [view addSubview:spinner];
    
    spinner.center = CGPointMake(width/2, 15);
    
    [self.navigationItem setRightBarButtonItem:[[UIBarButtonItem alloc] initWithCustomView:view] animated:YES];