Xcode Simulator Showing App as Blackscreen?

I’m having trouble being able to load my completed app from chapter 1 of the 5th Edition iOS programming book. Every time I hit play for simulate, the apple load screen appears and then the app opens but it opens to a black screen. Here is my code:

// Take2
// Copyright © 2016 Big Nerd Ranch. All rights reserved.

import UIKit

class ViewController: UIViewController {
override func viewDidLoad() {
@IBOutlet var questionlabel: UILabel!
@IBOutlet var answerlabel: UILabel!

let questions: [String] = ["From what is cognac made?",
                          "What is 7=7?",
                          "What is the capital of Vermont?",
                          "How old is Don?",
                          "What is Alex?"]
let answers: [String] = ["Grapes",
                         "A Little Boy"]
var currentQuestionIndex: Int = 0

@IBAction func showNextQuestion(sender: AnyObject){
    if currentQuestionIndex == questions.count{
        currentQuestionIndex == 0
    let question: String = questions[currentQuestionIndex]
    questionlabel.text = question
    answerlabel.text = "???"
@IBAction func showAnswer(sender: AnyObject){
    let answer:String = answers[currentQuestionIndex]
    answerlabel.text = answer