ios - Xcode 7 beta 2 and swift not getting along -

i have error when typed in code, gave me error. looks perfect, here code:

import uikit  class secondviewcontroller: uiviewcontroller {     @iboutlet weak var resultlabel: uilabel!     @iboutlet weak var temptext1: uitextfield!      @ibaction func converttemp1(sender: anyobject) {        #let fahrenheit = (temptext1.text nsstring).doublevalue         let celsius = (fahrenheit - 32 )/1.8         let resulttext = "celsius \(celsius)"         resultlabel.text = resulttext     }      override func viewdidload() {         super.viewdidload()         // additional setup after loading view, typically nib.     }      override func didreceivememorywarning() {         super.didreceivememorywarning()         // dispose of resources can recreated.     } } 

it give me following error: 'string?' not convertable 'nsstring' on line put # on. # not in real code.

note: not understand computer talk please try speak simply. :)

the text property of uitextfield returns optional string code doesn't handle optionals. casting nsstring isn't allowed there (also not necessary doublevalue).

you need handle optional. force-unwrap using !. can lead crashes. better use if let or guard let statements:

guard let fahrenheit = temptext1.text?.doublevalue else { return } 

for conciseness use optional chaining (the ?here). keep in 2 steps:

guard let fahrenheitstring = temptext1.text else { return } let fahrenheit = fahrenheitstring.doublevalue 

both equivalent.