EXC_BAD_INSTRUCTION斯威夫特(EXC_BAD_INSTRUCTION in Swi

我在斯威夫特全新的。 所以我做了这个教程做小费计算器，它能正常工作。 我开始一个新的项目，看看我是否能重建，保持原有的代码沿途参考。 我创建我的应用程序完全相同的方式，但使用不同的变量名。

我在lblABVCalculated.text行收到此错误：

线程1：EXC_BAD_INSTRUCTION（代码= EXC_I386_INVOP，子码=为0x0）

任何想法，为什么下面的代码将无法正常工作？

标题

import UIKit

class FirstViewController: UIViewController {

    @IBOutlet weak var txtOG: UITextField!
    @IBOutlet weak var txtFG: UITextField!
    @IBOutlet weak var lblABVCalculated: UILabel!

    var OG = ""
    var FG = ""
    var answer : Float = 0

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

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    @IBAction func btnCalculate(sender: UIButton) {
        calculateABV()
    }
    @IBAction func btnClear(sender: UIButton) {
        txtOG.text = ""
        txtFG.text = ""

        lblABVCalculated.text = "ABV"
    }

    func calculateABV() -> Bool {
        OG = txtOG.text
        FG = txtFG.text

        var fOG = (OG as NSString).floatValue
        var fFG = (FG as NSString).floatValue

        answer = fOG * (fFG * 0.01)

        var answerFormat : NSString = NSString(format: "%0.2f", answer)

        lblABVCalculated.text = "ABV: \(answerFormat)"
        // Thread 1: EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)

        return true
    }
}

文章来源: EXC_BAD_INSTRUCTION in Swift