我正在使用 Swift 2 和 Xcode 7 beta 6 开发应用程序。我正在尝试更改按钮的标题。我的代码：
print(randomNumber)
myButton.setTitle("\(randomNumber)", forState: UIControlState.Normal)
它给了我这个：致命错误：在展开可选值（lldb）时意外发现 nil
但是，当我打印 randomNumber 时，我得到了我想要的随机整数。我在我的代码中做错了什么？还是只是测试版的问题？
我的完整代码：
//
// ViewController.swift
// Math Practice
//
// Created by Pranav Wadhwa on 9/6/15.
// Copyright © 2015 Pranav Wadhwa. All rights reserved.
//
import UIKit
class ViewController: UIViewController {
var firstNumber = Int()
var secondNumber = Int()
var sign = String()
let arrayOfSigns = ["add", "subtract", "divide", "mulitply"]
var correctAnswer = Int()
var percentage = Int()
var buttonWithCorrectAnswer = Int()
var correct = Int()
var total = Int()
var timer = NSTimer()
var seconds = 0
var minutes = 0
var inSession = false
var firstRandomAnswer = Int()
var secondRandomAnswer = Int()
var thirdRandomAnswer = Int()
var fourthRandomAnswer = Int()
@IBOutlet var timerLabel: UILabel!
@IBOutlet var questionLabel: UILabel!
@IBOutlet var correctLabel: UILabel!
@IBOutlet var percentageLabel: UILabel!
@IBOutlet var button1: UIButton!
@IBOutlet var button2: UIButton!
@IBOutlet var button3: UIButton!
@IBOutlet var button4: UIButton!
@IBOutlet var startPause: UIButton!
@IBAction func startPause(sender: AnyObject) {
if inSession == false {
createQuestion()
inSession = true
print(startPause)
startPause.setTitle("Pause", forState: UIControlState.Normal)
timer = NSTimer.scheduledTimerWithTimeInterval(1, target: self, selector: Selector("updateTime"), userInfo: nil, repeats: true)
} else if inSession == true {
inSession = false
startPause.setTitle("Start", forState: UIControlState.Normal)
questionLabel.text = ""
button1.setTitle("", forState: UIControlState.Normal)
button2.setTitle("", forState: UIControlState.Normal)
button3.setTitle("", forState: UIControlState.Normal)
button4.setTitle("", forState: UIControlState.Normal)
timer.invalidate()
}
}
@IBAction func reset(sender: AnyObject) {
seconds = 0
minutes = 0
correct = 0
percentage = 0
total = 0
correctLabel.text = "0/0"
timerLabel.text = "00:00"
percentageLabel.text = "0%"
questionLabel.text = ""
button1.setTitle("", forState: UIControlState.Normal)
button2.setTitle("", forState: UIControlState.Normal)
button3.setTitle("", forState: UIControlState.Normal)
button4.setTitle("", forState: UIControlState.Normal)
timer.invalidate()
inSession = false
}
@IBAction func button1(sender: AnyObject) {
if buttonWithCorrectAnswer == 1 {
correct += 1
}
total += 1
createQuestion()
}
@IBAction func button2(sender: AnyObject) {
if buttonWithCorrectAnswer == 2 {
correct += 1
}
total += 1
createQuestion()
}
@IBAction func button3(sender: AnyObject) {
if buttonWithCorrectAnswer == 3 {
correct += 1
}
total += 1
createQuestion()
}
@IBAction func button4(sender: AnyObject) {
if buttonWithCorrectAnswer == 4 {
correct += 1
}
total += 1
createQuestion()
}
func updateTime() {
seconds += 01
if seconds == 60 {
minutes++
seconds = 0
}
if seconds < 10 {
timerLabel.text = "\(minutes):0\(seconds)"
} else {
timerLabel.text = "\(minutes):\(seconds)"
}
}
func createQuestion() {
if correct != 0 && total != 0 {
percentage = correct / total
}
correctLabel.text = "\(correct)/\(total)"
percentageLabel.text = "\(percentage)%"
firstNumber = Int(arc4random_uniform(39))
secondNumber = Int(arc4random_uniform(39))
firstNumber -= 20
secondNumber -= 20
let i = Int(arc4random_uniform(4))
sign = arrayOfSigns[i]
if sign == "divide" {
firstNumber = Int(arc4random_uniform(39))
secondNumber = Int(arc4random_uniform(39))
firstNumber -= 20
secondNumber -= 20
}
if sign == "add" {
questionLabel.text = "\(firstNumber) + \(secondNumber)"
correctAnswer = firstNumber + secondNumber
}
if sign == "subtract" {
questionLabel.text = "\(firstNumber) - \(secondNumber)"
correctAnswer = firstNumber - secondNumber
}
if sign == "divide" {
firstNumber = firstNumber * secondNumber
questionLabel.text = "\(firstNumber) / \(secondNumber)"
correctAnswer = firstNumber / secondNumber
}
if sign == "multiply" {
questionLabel.text = "\(firstNumber) * \(secondNumber)"
correctAnswer = firstNumber * secondNumber
}
createAnswers()
}
func createAnswers() {
buttonWithCorrectAnswer = Int(arc4random_uniform(4) + 1)
//Insert Correct Answer
if buttonWithCorrectAnswer == 1 {
button1.setTitle("\(correctAnswer)", forState: UIControlState.Normal)
} else if buttonWithCorrectAnswer == 2 {
button2.setTitle("\(correctAnswer)", forState: UIControlState.Normal)
} else if buttonWithCorrectAnswer == 3 {
button3.setTitle("\(correctAnswer)", forState: UIControlState.Normal)
} else if buttonWithCorrectAnswer == 4 {
button4.setTitle("\(correctAnswer)", forState: UIControlState.Normal)
}
//Setup Fake Answer
if sign == "add" || sign == "subtract" || sign == "divide" {
firstRandomAnswer = Int(arc4random_uniform(79))
firstRandomAnswer -= 40
print("Hello wold")
print(firstRandomAnswer)
secondRandomAnswer = Int(arc4random_uniform(79))
secondRandomAnswer -= 40
while secondRandomAnswer == firstRandomAnswer {
secondRandomAnswer = Int(arc4random_uniform(79))
secondRandomAnswer -= 40
}
thirdRandomAnswer = Int(arc4random_uniform(79))
thirdRandomAnswer -= 40
while thirdRandomAnswer == secondRandomAnswer || thirdRandomAnswer == firstRandomAnswer {
thirdRandomAnswer = Int(arc4random_uniform(79))
thirdRandomAnswer -= 40
}
fourthRandomAnswer = Int(arc4random_uniform(79))
fourthRandomAnswer -= 40
while fourthRandomAnswer == thirdRandomAnswer || fourthRandomAnswer == secondRandomAnswer || fourthRandomAnswer == firstRandomAnswer {
fourthRandomAnswer = Int(arc4random_uniform(79))
fourthRandomAnswer -= 40
}
}
if sign == "multiply" {
firstRandomAnswer = Int(arc4random_uniform(799))
firstRandomAnswer -= 400
secondRandomAnswer = Int(arc4random_uniform(799))
secondRandomAnswer -= 400
while secondRandomAnswer == firstRandomAnswer {
secondRandomAnswer = Int(arc4random_uniform(799))
secondRandomAnswer -= 400
}
thirdRandomAnswer = Int(arc4random_uniform(799))
thirdRandomAnswer -= 400
while thirdRandomAnswer == secondRandomAnswer || thirdRandomAnswer == firstRandomAnswer {
thirdRandomAnswer = Int(arc4random_uniform(799))
thirdRandomAnswer -= 400
}
fourthRandomAnswer = Int(arc4random_uniform(799))
fourthRandomAnswer -= 400
while fourthRandomAnswer == thirdRandomAnswer || fourthRandomAnswer == secondRandomAnswer || fourthRandomAnswer == firstRandomAnswer {
fourthRandomAnswer = Int(arc4random_uniform(799))
fourthRandomAnswer -= 400
}
}
//Insert Fake Answers
if buttonWithCorrectAnswer != 1 {
button1.setTitle("\(firstRandomAnswer)", forState: UIControlState.Normal)
}
if buttonWithCorrectAnswer != 2 {
button2.setTitle("\(secondRandomAnswer)", forState: UIControlState.Normal)
}
if buttonWithCorrectAnswer != 3 {
button3.setTitle("\(thirdRandomAnswer)", forState: UIControlState.Normal)
}
if buttonWithCorrectAnswer != 4 {
button4.setTitle("\(fourthRandomAnswer)", forState: UIControlState.Normal)
}
}
@IBOutlet var backgroundImage: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
var image = arc4random_uniform(2)
image++
backgroundImage.image = UIImage(named: "background_" + String(image))
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}