这是为xcode 6.2编写的本书中的编码和示例示例的新增功能，而我拥​​有最新版本。

Question

I get the following error when I run the app and try and click any key on the keypad that opens on launch. Here is the error I get in the attached photo

Below is my code and it highlights the first func at the bottom called func formatAsCurrancy... as the problem area. I have converted all the old code in the book as it prompted me to. Not sure what to do at this point. Thank you for any help.

import UIKit

class ViewController: UIViewController {
    //properties for programmatically interacting with UI components
    @IBOutlet weak var billAmountLabel: UILabel!
    @IBOutlet weak var customTipPercentLabel1: UILabel!
    @IBOutlet weak var customTipPercentageSlider: UISlider!
    @IBOutlet weak var customTipPercentLabel2: UILabel!
    @IBOutlet weak var tip15Label: UILabel!
    @IBOutlet weak var total15Label: UILabel!
    @IBOutlet weak var tipCustomLabel: UILabel!
    @IBOutlet weak var totalCustomLabel: UILabel!
    @IBOutlet weak var inputTextField: UITextField!

    // NSDecimalNumber constants used in the calculateTip method
    let decimal100 = NSDecimalNumber(string: "100.0")
    let decimal15Percent = NSDecimalNumber(string: "0.15")

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        // select inputTextField so keypad displays when the view loads 
        inputTextField.becomeFirstResponder()
    }

    @IBAction func calculateTip(_ sender: Any) {
        let inputString = inputTextField.text //get user input

        // convert slider value to an NSDecimalNumber
        let sliderValue =
            NSDecimalNumber(integerLiteral: Int(customTipPercentageSlider.value))

        // divide sliderValue by decimal100 (100.0) to get tip %
        let customPercent = sliderValue / decimal100

        // did customTipPercentageSlider generate the event?
        if sender is UISlider {
            // thumb moved so update the Labels with new custom percent
            customTipPercentLabel1.text =
                NumberFormatter.localizedString(from: customPercent,
                                                number: NumberFormatter.Style.percent)
            customTipPercentLabel2.text = customTipPercentLabel1.text
        }

        // if there is a bill amount, calculate tips and totals
        if !(inputString?.isEmpty)! {
            // convert to NSDecimalNumber and insert decimal point
            let billAmount =
                NSDecimalNumber(string: inputString) / decimal100

            // did inputTextField generate the event?
            if sender is UITextField {
                billAmountLabel.text = " " + formatAsCurrency(number: billAmount)

                // calculate and display the 15% tip and total
                let fifteenTip = billAmount * decimal15Percent
                tip15Label.text = formatAsCurrency(number: fifteenTip)
                total15Label.text =
                    formatAsCurrency(number: billAmount + fifteenTip)
                }

            // calculate custom tip and display custom tip and total
            let customTip = billAmount * customPercent
            tipCustomLabel.text = formatAsCurrency(number: customTip)
            totalCustomLabel.text =
                formatAsCurrency(number: billAmount + customTip)
        }
        else {// clear all Labels
            billAmountLabel.text = ""
            tip15Label.text = ""
            total15Label.text = ""
            tipCustomLabel.text = ""
            totalCustomLabel.text = ""
        }
    }

}

// convert a numeric value to localized currency string 
func formatAsCurrency(number: NSNumber) -> String {
    return NumberFormatter.localizedString(
        from: number, number: NumberFormatter.Style.currency)
}
// overloaded + operator to add NSDecimalNumbers
func +(left: NSDecimalNumber, right: NSDecimalNumber) -> NSDecimalNumber {
    return left.adding(right)
}
// overloaded * operator to multiply NSDecimalNumbers
func *(left: NSDecimalNumber, right: NSDecimalNumber) -> NSDecimalNumber {
    return left.multiplying(by: right)
}
// overloaded / operator to divide NSDecimalNumbers
func /(left: NSDecimalNumber, right: NSDecimalNumber) -> NSDecimalNumber {
    return left.dividing(by: right)
}

Answer 1

The simulator is trying to find a numeric keyboard on your computer, but your computer shouldn't have one so that's why it's giving you the error.

If you go to the simulator and then Hardware -> Keyboard -> Uncheck use hardware keyboard, the issue will go away.