How to determine a struct's return value based on UI Objects - swift

Question

I currently have a struct in which my ViewController references to return a random value from a group of arrays (aList, bList, cList, & dList). I ideally would like to be have aList always enabled while being able to toggle bList, cList, & dList on/off.
I have all this in a struct (shown below) but I'm very new to Swift and am learning that structs are "value types" while the ViewController is a "reference type" and apparently UI objects can only be referenced from reference types?
import GameKit
import Foundation
struct PromptProvider {
var aListIndex = 0
var bListIndex = 0
var cListIndex = 0
var dListIndex = 0
var includeB = false
var includeC = false
var includeD = false
var aList = [
“A1”,
“A2”,
“A3”,
“A4”]
var bList = [
“B1”,
“B2”,
“B3”,
“B4”]
var cList = [
“C1”,
“C2”,
“C3”,
“C4”]
var dList = [
“D1”,
“D2”,
“D3”,
“D4”]
init() {
self.restart()
}
mutating func restart() {
if includeB == true {self.aList.append(contentsOf: bList)}
if includeC == true {self.aList.append(contentsOf: cList)}
if includeD == true {self.aList.append(contentsOf: dList)}
self.aList.shuffle()
self.aListIndex = 0
}
mutating func randomPrompt() -> String {
if aListIndex == aList.count {
return "Out of String Values"
}
else {
defer {aListIndex += 1}
return aList[aListIndex]
}
}
}
I think I'm treating the struct as a reference type here but am unable to connect a UI object to the structs code.
Any help/guidance on how to pivot my strategy with this would be greatly appreciated. Thank you

Answer 1

As long as you have a single instance of PromptProvider you can make changes to that instance at will. If you need multiple references to a PromptProvider then you will need to make PromptProvider a class.
I mentioned that you had a bug in your restart method. You were appending data to your aList array without clearing out the previous appended data. What you need is a master list to contain your aList as well as the contents of your other lists so you can reset it as needed.
If I were you, I'd implement your PromptProvider struct like this:
struct PromptProvider {
let aList = [
"A1",
"A2",
"A3",
"A4"]
let bList = [
"B1",
"B2",
"B3",
"B4"]
let cList = [
"C1",
"C2",
"C3",
"C4"]
let dList = [
"D1",
"D2",
"D3",
"D4"]
var includeB = false {
didSet { restart() }
}
var includeC = false {
didSet { restart() }
}
var includeD = false {
didSet { restart() }
}
var masterList: [String] = []
init() {
self.restart()
}
mutating func restart() {
masterList.removeAll()
masterList.append(contentsOf: aList)
if includeB == true {masterList.append(contentsOf: bList)}
if includeC == true {masterList.append(contentsOf: cList)}
if includeD == true {masterList.append(contentsOf: dList)}
masterList.shuffle()
}
mutating func randomPrompt() -> String? {
return masterList.popLast()
}
}
And then in your view controller you can declare and use your PromptProvider like so:
class ViewController: UIViewController {
var promptProvider = PromptProvider()
#IBAction func onPrintRandomPrompt(_ sender: UIButton) {
if let prompt = promptProvider.randomPrompt() {
print(prompt)
} else {
print("Out of String Values")
promptProvider.restart()
}
}
}
If you want to change the contents of the provider all you have to do is toggle its flags and that will reset the contents of the master list.
extension ViewController {
#IBAction func onIncludeB(_ sender: UIButton) {
promptProvider.includeB.toggle()
sender.setTitleColor(promptProvider.includeB ? .green : .red, for: .normal)
}
#IBAction func onIncludeC(_ sender: UIButton) {
promptProvider.includeC.toggle()
sender.setTitleColor(promptProvider.includeC ? .green : .red, for: .normal)
}
#IBAction func onIncludeD(_ sender: UIButton) {
promptProvider.includeD.toggle()
sender.setTitleColor(promptProvider.includeD ? .green : .red, for: .normal)
}
}