animated error

gistfile1.m

- (void)showError;
{
    dispatch_async( dispatch_get_main_queue(), ^ {
        // Setup error view; these values are visible as it slides into place.
        _errorView.alpha = finalErrorAlpha;
        _errorLabel.text = [_error localizedDescription];
        // Slide down the error view, with normal alpha.
        [UIView animateWithDuration: slideDownDuration
                         animations: ^{
                             CGRect frame = _errorView.frame;
                             frame.origin.y = topMargin;
                             _errorView.frame = frame;
                         }
                         completion: ^void(BOOL finished) {
                             // Pulse the alpha stronger.
                             [UIView animateWithDuration: fadeInDuration
                                              animations: ^{
                                                  _errorView.alpha = strongErrorAlpha;
                                              }
                                              completion: ^void(BOOL finished2) {
                                                  // Back off on the alpha to the normal level.
                                                  [UIView animateWithDuration: lessBrightDuration
                                                                   animations: ^{
                                                                       _errorView.alpha = finalErrorAlpha;
                                                                   }];
                                              }];
                         }];
    });
}

This is the drawback to blocks: Unless you're willing to use assign your code to variables, you end up with heavily indented code and duplicate parameter names.