How do I loop back to the first item in an Array? - arrays

Question

I'm sure this is very simple, but I'm using a button to go to the next item in an array and display it in a label. That much works just fine, however once the end of the array is reached the app crashes since there are no items left to display. How do I get it to go back to the first item? I've tried an If statement but had no luck.
import UIKit
class ViewController: UIViewController {
var firstQuote = 0
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBOutlet weak var quotesLabel: UILabel!
var quotes = ["","Quote 1", "Quote 2", "Quote 3"]
#IBAction func nextButton(_ sender: UIButton) {
firstQuote = firstQuote + 1
quotesLabel.text = quotes[firstQuote]
}
}
This is the If Statement I tried
#IBAction func nextButton(_ sender: UIButton) {
if firstQuote < quotes.count{
firstQuote = firstQuote + 1
quotesLabel.text = quotes[firstQuote]
}
if firstQuote == quotes.count{
firstQuote = 0
quotesLabel.text = quotes[firstQuote]
}
}

Answer 1

A common solution is to use % (the remainder operator) to wrap firstQuote back to 0 when it is equal to quotes.count:
firstQuote = (firstQuote + 1) % quotes.count

Answer 2

This works for me😁
class ViewController: UIViewController {
var quotes = ["Quote 0","Quote 1", "Quote 2", "Quote 3"]
var quotesNum = 0
#IBOutlet weak var result: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
result.text = quotes[quotesNum]
}
#IBAction func incrementButton(_ sender: Any) {
if quotesNum < quotes.count {
quotesNum += 1
if quotesNum == quotes.count {
quotesNum = 0
}
result.text = quotes[quotesNum]
}
}

Answer 3

With This Code Beside Fixing Your Problem, You Can Understand How property observer Can Work
class ViewController: UIViewController {
var quotes = ["Quote 0","Quote 1", "Quote 2", "Quote 3"]
var quotesNum: Int = 0 {
didSet {
result.text = quotes[quotesNum]
}
}
#IBOutlet weak var result: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
result.text = quotes[quotesNum]
}
#IBAction func incrementButton(_ sender: Any) {
if quotesNum < quotes.count - 1 {
if quotesNum == quotes.count - 1 {
quotesNum = 0
} else {
quotesNum += 1
}
} else {
quotesNum = 0
}
}