线程1: EXC_BAD_INSTRUCTIONS = SWIFT

Question

当我启动应用程序时，它运行正常。当我单击随机化按钮时，线程1: EXC_BAD_INSTRUCTIONS出现在finalLABEL.text = str点。致命错误:在展开可选值时意外找到零

@IBOutlet var fromACT: UITextField!
@IBOutlet var toEXT: UITextField!
@IBOutlet var finalLABEL: UILabel!
func unsafeRandomIntFrom(start: Int32, to end: Int32) -> Int32 {
    let number =  Int32(arc4random_uniform(UInt32(end - start + 1))) + start
    return number
}

@IBAction func random(sender: AnyObject) {
    let convertedNumber = NSString(string: fromACT.text!).intValue
    let convertedNumber2 = NSString(string: toEXT.text!).intValue
    let randomSV = unsafeRandomIntFrom(convertedNumber, to: convertedNumber2)
    let str = String(randomSV)

    finalLABEL.text? = str
}

Answer 1

试图保护您的代码：

...
let convertedNumber = NSString(string: fromACT.text!).intValue
let convertedNumber2 = NSString(string: toEXT.text!).intValue
let randomSV = unsafeRandomIntFrom(convertedNumber, to: convertedNumber2)
if Int(randomSV) != nil {
    let str = String(randomSV)
    finalLABEL.text? = str
}

还可以为函数设置默认值：

func unsafeRandomIntFrom(start: Int32 = 3, to end: Int32 = 6) -> Int32 {
    let number =  Int32(arc4random_uniform(UInt32(end - start + 1))) + start
    return number
}

若要确保在不带值的情况下调用函数时，必须具有默认值。