UserDefaults won't retrieve my string array correctly

Question

I am trying to make a mechanism that lets users save items to favourites (which is an array) and then save that to UserDefaults, however I can't seem to get it to write to UD correctly. Printing UDSaved in the example below returns [], even though I just appended an element to the array.

Does anyone have an idea what I'm doing wrong?

Is it a syntax error and I am not retrieving this correctly or is there a problem with my logic?

var favouritesArray: [String] = []

func UDWrite() {UserDefaults.standard.set(favouritesArray, forKey: "UDfavouritesArray")}
let UDSaved = UserDefaults.standard.stringArray(forKey: "UDfavouritesArray") ?? [String]()


favouritesArray.append("element")
UDWrite()

print(UDSaved)

You don’t appear to be re-reading UDSaved after you have updated the defaults. — Nick
– Nick, Commented Jun 24, 2018 at 12:45
you are saving empty array and then getting it, after that adding string, try to add favouritesArray.append("element"), right after var favouritesArray: [String] = [] — Arslan Asim
– Arslan Asim, Commented Jun 24, 2018 at 12:45
You do the following: Create an empty array a. Write a to a dictionary. Create an array b by reading a from a dictionary. Append something to a. Print b. — MechMK1
– MechMK1, Commented Jun 24, 2018 at 12:46
@DavidStockinger the function to write a to the dictionary is not called after a is created, it's called after I append something to a. So the order would be: - create an empty array A - create an array B by reading A from the dictionary - append something to A - write A to the dictionary B I realise though I need to assign B the value of A as part of my function, and this seems to work. — CristianMoisei
– CristianMoisei, Commented Jun 24, 2018 at 12:53

Herr der Töne · Accepted Answer · 2018-06-24 12:53:28Z

3

As some stated in the comments: UDSaved never get's updated. My solution would be to make UDSaved a function like so:

var favouritesArray: [String] = []

func UDWrite() {UserDefaults.standard.set(favouritesArray, forKey: "UDfavouritesArray")}
func UDSaved() -> [String] {return UserDefaults.standard.stringArray(forKey: "UDfavouritesArray") ?? [String]}()

favouritesArray.append("element")
UDWrite()

print(UDSaved())

Or you could make it a computed property

var UDSaved: [String] {
   return UserDefaults.standard.stringArray(forKey: "UDfavouritesArray") ?? [String]
}

answered Jun 24, 2018 at 12:53

Herr der Töne

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4 Comments

CristianMoisei Over a year ago

Thank you, and everyone who commented. I understand my mistake now and I fixed it by adding UDSaved = favouritesArray to my UDWrite() function and this fixed the problem.

Herr der Töne Over a year ago

Well UDSaved = favouritesArray helps as long as your app is running but this won't help to restore state after relaunching your app!

David Pasztor Over a year ago

@CristianMoisei I'd highly recommend not doing that. When you can avoid modifying external variables inside functions, you should do so to keep your functions pure. Making UDSaved a computed property is a much better solution.

CristianMoisei Over a year ago

You're right @HerrderTöne I'll take some time to wrap my head around your solution (I'm relatively new to this) and do it that way. Thanks again.

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