https://stackoverflow.com/questions/24005678/what-is-the-equivalent-of-an-objective-c-id-in-swift

Swift 3

Any, if you know the sender is never nil.

@IBAction func buttonClicked(sender : Any) {
println(“Button was clicked”, sender)
}
Any?, if the sender could be nil.

@IBAction func buttonClicked(sender : Any?) {
println(“Button was clicked”, sender)
}