saving array data as user default and loading array in table view - arrays

Question

I created an array and I'm populating the data (type Double) onto a table view. But when the app closes, all the data goes away! Im having trouble saving the array as a User Default so that when the user closes the app and opens it again, all of the info is still populated and available to see.
I set up an array called moneySpentArray, and this array holds all of a users entered transactions. After user clicks "submit", the IB action takes the input and sends it thru a function called addToMoneySpentArray
#IBAction func submitNewInfo(_ sender: UIButton) {
AddSubtractMoneyController.addToMoneySpentArray(amountISpent: Double(outputLabel.text!)!)
}
Below is the addToMoneySpentArray function that I send the data too, which then appends that amount into the 'moneySpentArray'.
class func addToMoneySpentArray( amountISpent: Double) {
moneySpentArray.append(amountISpent)
print(moneySpentArray)
}
Now in my SpendingHistoryVC- when the View loads, I use the array.reduce to add up the sum of the values in the array and display it in a text label called "youSpentThisMuch"- and Below this label will be the table view, which holds all the individual indexed amounts from the array also. Im confused on where and when to implement user defaults so that when a user enters a new amount through the IBAction above, it automatically stores and updates the array as a new user default. So even if the app is closed, their array history is still available to see.
override func viewDidLoad() {
super.viewDidLoad()
let arraySum: Double = AddSubtractMoneyController.moneySpentArray.reduce(0.0, +)
youSpentLabel.text = "\(arraySum)"
}

Answer 1

In addToMoneySpentArray save the data:
class func addToMoneySpentArray( amountISpent: Double) {
moneySpentArray.append(amountISpent)
UserDefaults.standard.set(moneySpentArray, forKey: "moneySpent")
print(moneySpentArray)
}
and in viewDidLoad load it
override func viewDidLoad() {
super.viewDidLoad()
let moneySpentArray = UserDefaults.standard.array(forKey: "moneySpent") as? [Double] ?? [Double]()
AddSubtractMoneyController.moneySpentArray = moneySpentArray
let arraySum = moneySpentArray.reduce(0.0, +)
youSpentLabel.text = "\(arraySum)"
}