Ios 在展开可选值时意外发现nil

我对编程非常陌生，几天来我一直在网上寻找，试图解决这个问题，我一直在用我的Swift编程。我对这一切都是陌生的；而且，我已经尽了最大的努力，试图自己找到一个解决办法。但是，在经历了这段令人沮丧的时间后，我认为可以问问专家

我尝试使用的代码如下：

import UIKit
class ViewController: UIViewController {

    var myTime: AnyObject = NSUserDefaults() //creates a var called myTime that can be used to save the time parameter.
    var timer = NSTimer() // creates a variable used by the timer loop.

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        myTime = NSUserDefaults.standardUserDefaults().objectForKey("two")! //sets timer value to last saved value

        if (myTime as NSNumber == 0){ //if the initial value doesnt exhist the if statement creates one.
            NSUserDefaults.standardUserDefaults().setInteger(0, forKey: "two") //sets timer to zero and saves parameter
        }

        timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("action"), userInfo: nil, repeats: true) // Creates a timer at 1 second time interval which then performs function called 'action' and will continue until boolean is set to false or NSTimer is invalidated.
    }

    func action(){

        myTime = Int(myTime as NSNumber) + 1 // increases myTime by 1
        println(myTime) //println(time) // prints myTime

        NSUserDefaults.standardUserDefaults().setInteger(myTime as Int, forKey: "two") // saving variable two with value of 2
        NSUserDefaults.standardUserDefaults().synchronize() // Added synchronize as suggested by LAMMERT WESTERHOFF
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}

我收到的错误消息如下：

致命错误：在展开可选值时意外发现nil （lldb）

说：

线程1:EXC_BAD_指令（代码=EXC_1386_INVOP，子代码=0x0）

如果有人能告诉我我做错了什么以及如何解决我的问题，我将不胜感激。

错误发生在这里

myTime = NSUserDefaults.standardUserDefaults().objectForKey("two")!

这是因为您试图将可选值（不能为nil）分配给非可选变量

要解决此问题，需要先为键“2”设置对象，然后才能获取此对象或使myTime变量成为可选变量

此外，要检查该值，在将其转换为NSNumber之前，应检查其是否为nil

这段代码应该可以正常工作

*import UIKit
class ViewController: UIViewController {

//here I added ? which means optional value
    var myTime: AnyObject? = NSUserDefaults() //creates a var called myTime that can be used to save the time parameter.
    var timer = NSTimer() // creates a variable used by the timer loop.

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

// here I removed ! because value for key "two" may not been set so it is optional value
        myTime = NSUserDefaults.standardUserDefaults().objectForKey("two") //sets timer value to last saved value

//here we check myTime object for nil before converting to NSInteger and checking for 0
        if ( myTime == nil || myTime as NSNumber == 0){ //if the initial value doesnt exhist the if statement creates one.
            NSUserDefaults.standardUserDefaults().setInteger(0, forKey: "two") //sets timer to zero and saves parameter
        }

        timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("action"), userInfo: nil, repeats: true) // Creates a timer at 1 second time interval which then performs function called 'action' and will continue until boolean is set to false or NSTimer is invalidated.
    }

    func action(){

        myTime = Int(myTime as NSNumber) + 1 // increases myTime by 1
        println(myTime) //println(time) // prints myTime

        NSUserDefaults.standardUserDefaults().setInteger(myTime as Int, forKey: "two") // saving variable two with value of 2
        NSUserDefaults.standardUserDefaults().synchronize() // Added synchronize as suggested by LAMMERT WESTERHOFF
    }
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
}*

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您不会说哪一行给了您错误，但是考虑到您第一次运行代码时，用户默认中没有条目。这让我觉得问题出在

.objectForKey（“两个”）。你不能保证会有这样一个物体。谢谢你对谢尔盖的巨大帮助。它完全解决了我的问题。