What are block-based animation methods in iPhone OS 4.0?

I am trying to implement a game using the iPhone OS 4.0 (iOS4?) SDK. In the previous versions of the SDK, I've been using the [UIView beginAnimations:context:] and [UIView commitAnimations] to create some animations. However, when I look at the documentation of the functions in 4.0, I see this comment.

> Use of this method is discouraged in > iPhone OS 4.0 and later. You should > use the block-based animation methods > instead.

You can find it here: http://developer.apple.com/iphone/library/documentation/uikit/reference/UIView_Class/UIView/UIView.html#//apple_ref/occ/clm/UIView/commitAnimations

My question is, what are block-based animations in iPhone OS 4.0? I though that the beginAnimations:context: and commitAnimations functions were used to create animation blocks..

I have posted an example in my blog:

	CGPoint originalCenter = icon.center;
	[UIView animateWithDuration:2.0
			animations:^{ 
				CGPoint center = icon.center;
				center.y += 60;
				icon.center = center;
			} 
			completion:^(BOOL finished){

				[UIView animateWithDuration:2.0
						animations:^{ 
							icon.center = originalCenter;
						} 
						completion:^(BOOL finished){
							;
						}];
		
			}];

The above code will animate a UIImageView* (icon) in a 2-second animation. Once completed, another animation will move the icon back to it’s original position.

If you follow that link and scroll up a bit, you will see animate methods new to ios4.

animateWithDuration:animations:
animateWithDuration:animations:completion:
animateWithDuration:delay:options:animations:completion:

There are also some related transition methods. For each of these, the animations argument is a block object:

> animations
> A block object containing > the changes to commit to the views. > This is where you programmatically > change any animatable properties of > the views in your view hierarchy. This > block takes no parameters and has no > return value. This parameter must not > be NULL.

Block objects are part of Concurrent Programming

Here's a very simple example. The code just fades out an UIView and hides it after the animation is done:

[UIView animateWithDuration:1.0 
                      delay:0.0 
                    options:UIViewAnimationOptionCurveEaseInOut 
                 animations:^ {
                     bgDisplay.alpha = 0.0;
                 } 
                 completion:^(BOOL finished) {
                     bgDisplay.hidden = YES;
                 }];

or in different formatting:

[UIView animateWithDuration:1.0 delay:0.0 options:UIViewAnimationOptionCurveEaseInOut animations:^ {
    bgDisplay.alpha = 0.0;
} completion:^(BOOL finished) {
    bgDisplay.hidden = YES;
}];