importUIKit

classViewController:UIViewController{

@IBOutletweakvardisplay:UILabel!

varuserIsInputingDigit:Bool=false
@IBActionfuncappendDigit(sender:UIButton){
letdigit=sender.currentTitle!
ifuserIsInputingDigit{
display.text=display.text!+digit

}else{

display.text=digit
userIsInputingDigit=true
}

}

overridefuncviewDidLoad(){
super.viewDidLoad()
//Doanyadditionalsetupafterloadingtheview,typicallyfromanib.
}



}

来自： https://itunes.apple.com/us/course/developing-ios-8-apps-swift/id961180099