Question

我将一个长数字作为字符串从FirstVC.swift传递给SecondVC.swift，如：

let userId = user.userID // GOT FROM GOOGLE SIGN IN

let vc = self.storyboard?.instantiateViewController(withIdentifier: "SecondVC") as! SecondVC
let navigationController = self.tabBarController?.navigationController
vc.socid = userId!
let transition = CATransition()
transition.duration = 0.3
transition.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
transition.type = kCATransitionMoveIn
transition.subtype = kCATransitionFromTop
self.navigationController?.view.layer.add(transition, forKey: nil)
self.navigationController?.pushViewController(vc, animated: false)

并在SecondVC.swift收到：

var socid:String!

override func viewDidLoad() {
    super.viewDidLoad()

    print(socid) // RETURNS Optional("11365489964475")

    if(socid==nil){
        print("socid is empty")
    }else{
        let i1 = Int(socid!)! + 7778955 //I GET ERROR HERE
    }

}

但我收到错误：主题1：致命错误：在解包可选值时意外发现nil

如果socid有可选值，为什么我无法打开字符串？ AND 当socid等于其他一些短号时，一切正常。

Answer 1

因为将字符串转换为int失败而崩溃：

let i1 = Int(socid!)! + 7778955

如果Int(bigthing)失败，则为零。

Answer 2

let socid = ""

override func viewDidLoad() {
    super.viewDidLoad()

   let mySocid = Int(socid)

    guard let mySocid2 = mySocid else {
        return
    }
    let newValue = mySocid2 + 50

    print("newValue\(newValue)")
    // Do any additional setup after loading the view, typically from a nib.
}

Answer 3

对我来说，你的代码有效，但我认为避免强制解包是一个好习惯。也许做这样的事情：

if let socid = socid, let socidInt = Int(socid) {
  let i1 = socidInt + 7778955
  print(i1)
} else {
  print("Failed to unwrap socid to an integer")
}

Answer 4

试试这个......

override func viewDidLoad() {
    super.viewDidLoad()

    if let socid = socid, var i1 = Int(socid)
    {
        i1 += 7778955
        print("Te number is \(number)")
    }
}

字符串存在时获取nil

4 个答案: