Save a tuple in NSUserDefaults

Question

I'm using a tuple to store something like this.

var accessLavels: (hasInventoryAccess: Bool, hasPayrolAccess: Bool)
accessLavels = (hasInventoryAccess: true, hasPayrolAccess: false)

Now I want to save it in NSUserDefaults.

NSUserDefaults.standardUserDefaults().setValue(accessLavels, forKey: "AccessLevelKey")
NSUserDefaults.standardUserDefaults().synchronize()

But I get the following error.

Type '(hasInventoryAccess: Bool, hasPayrolAccess: Bool)' does not conform to protocol 'AnyObject'

How can I resolve this issue? If its impossible, then any other suggestions to save a tuple is welcome.

Thank you.

Answer 1

I encountered a similar scenario trying to encode a tuple with NSCoder. The way I am solving it is by manually converting the tuple to a Dictionary. This is not a great solution as the keys need to be changed in several places if the tuple ever changes.

I had a nested enum in my tuple and gave it a base type (String) from which I converted the raw value. It was a little extra work but thankfully yours is only primitives.

# SerializeableTuple.swift

typealias AccessTuple = (hasInventoryAccess: Bool, hasPayrolAccess: Bool)
typealias AccessDictionary = [String: Bool]

let InventoryKey = "hasInventoryAccess"
let PayrollKey = "hasPayrollAccess"

func serializeTuple(tuple: AccessTuple) -> AccessDictionary {
    return [
        InventoryKey : tuple.hasInventoryAccess,
        PayrollKey : tuple.hasPayrolAccess
    ]
}

func deserializeDictionary(dictionary: AccessDictionary) -> AccessTuple {
    return AccessTuple(
        dictionary[InventoryKey] as Bool!,
        dictionary[PayrollKey] as Bool!
    )
}

---

# Encoding / Decoding

var accessLavels: AccessTuple = (hasInventoryAccess: true, hasPayrolAccess: false)

// Writing to defaults
let accessLevelDictionary = serializeTuple(accessLavels)
NSUserDefaults.standardUserDefaults().setObject(accessLevelDictionary, forKey: "AccessLevelKey")

// Reading from defaults
let accessDic = NSUserDefaults.standardUserDefaults().dictionaryForKey("AccessLevelKey") as AccessDictionary
let accessLev = deserializeDictionary(accessDic)

Answer 2

You can store Bool, Float, Int, Object, Double or URL but not a Tuple. So you have two options, save two only hasPayrolAccess and hasPayrolAccess Bool values:

NSUserDefaults.standardUserDefaults().setBool(true, forKey: "hasInventoryAccess")
NSUserDefaults.standardUserDefaults().setBool(false, forKey: "hasPayrolAccess")
let hasInventoryAccess  = NSUserDefaults.standardUserDefaults().boolForKey("hasInventoryAccess")
println(hasInventoryAccess)

let hasPayrolAccess  = NSUserDefaults.standardUserDefaults().boolForKey("hasPayrolAccess")
println(hasPayrolAccess)

Or save it using an Array of Bool:

var accessLavels = [true,false]
println(accessLavels)
NSUserDefaults.standardUserDefaults().setValue(accessLavels, forKey: "accessLavels")
if let loadAccessLavels = NSUserDefaults.standardUserDefaults().arrayForKey("accessLavels") as? [Bool] {
    if let hasInventoryAccess = loadAccessLavels.first {
        println(hasInventoryAccess)
    }
    if let hasPayrolAccess = loadAccessLavels.last {
        println(hasPayrolAccess)
    }
}

Answer 3

I had a tuple with 3 values.

The following code was used for saving the tuple. Basically, I created a string from tuple (with components separated by a comma).

let defaultsLoad = NSUserDefaults.standardUserDefaults()
if appSingleton.runwayDestShared != nil
{
   // Creating a String from the tuple
   let runwayDestString = appSingleton.runwayDestShared!.0 + "," + appSingleton.runwayDestShared!.1  + "," + appSingleton.runwayDestShared!.2
   defaultsLoad.setObject(runwayDestString, forKey: "RunwayDest")
}

To retrieve the tuple, I retrieved the string, broke it into array and used the array to re-create a tuple.

let runwayDestString = defaultsLoad.stringForKey("RunwayDest")
if let runwayDestString = runwayDestString
{
    let runwayDestArray = runwayDestString.componentsSeparatedByString(",")
    appSingleton.runwayDestShared = (runwayDestArray[0],runwayDestArray[1],runwayDestArray[2])
}