UIView Animations

[UIView animateWithDuration:1.0
    animations:^{
        someView.alpha = 0;
        otherView.alpha = 1;
    }
    completion:^(BOOL finished) {
    [someView removeFromSuperview];
}];

The carat “^” character defines a block. For example, ^{ … } is a block. More specifically, it is a block that returns “void” and accepts no arguments. It is equivalent to a method such like: “- (void)something;” but there is no inherent name associated with the code block.

Define a block that can accept arguments work very similarly. To supply an argument to a block, you define the block like so: **^(BOOL someArg, NSString* someStr) { … }**. When you use API calls that support blocks, you’ll be writing blocks that look similar to this, especially for animation blocks or NSURLConnection blocks as shown in the above example.