斯威夫特3

Any,如果你知道发件人永远不会nil.

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

Any?,如果发件人可以nil.

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

斯威夫特2

AnyObject,如果你知道发件人永远不会nil.

@IBAction func buttonClicked(sender : AnyObject) {
    println("Button was clicked", sender)
}

AnyObject?,如果发件人可以nil.

@IBAction func buttonClicked(sender : AnyObject?) {
    println("Button was clicked", sender)
}