An example of how UIViewAnimationOptionLayoutSubviews works?

Apple's documentation describes UIViewAnimationOptionLayoutSubviews as:

Lay out subviews at commit time so that they are animated along with their parent.

Here is a sample of the code I'm interested in. I wish to animate the -layoutSubviews of detailView; however, it doesn't seem to layout the subviews of detailView, so I'm not sure what effect it actually has.

    void (^animation) () = ^
    {
        [self.detailView setNeedsLayout];
        [self.detailView layoutIfNeeded];
    };

    [UIView animateWithDuration:0.5
                          delay:0.0
                        options:UIViewAnimationOptionLayoutSubviews
                     animations:^{
                         animation();
                     }
                     completion:nil];