Learning Swift™ Programming

Trailing Closures

When you write a closure as a parameter of a function, the closure is often the last parameter. You see this often in Objective-C as well with blocks. In Objective-C, you write something like this when animating:

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 [UIView animateWithDuration:1.50 delay:0options:(UIViewAnimationOptionCurveEaseOut|UIViewAnimationOptionBeginFromCurrentState)animations:^{    //do animations here.}];

Notice that this function takes two blocks, and you have one block at the end. You could write the last block as a trailing closure. This means you could write the closure outside the function’s closing parentheses. You could rewrite the last function in Swift like so:

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UIView.animateWithDuration(1.50) ...