Retrieve array function not working

Question

I created two functions called save array and retrieve array and their job is to save and retrieve an array from the phone. My problem is that they are not working. These are the two functions.

func SaveArray (array: [IOU],fileID: String){
NSKeyedArchiver.archiveRootObject(array, toFile: fileID)
}
func RetrieveArray (fileID: String, var array: [IOU]) -> [IOU]{
    if let arraytoRetrieve = NSKeyedUnarchiver.unarchiveObjectWithFile(fileID) as? [IOU]{
        array = arraytoRetrieve
    }
    return array
}

IOU is a class I have defined like this:

class IOU : NSObject, NSCoding {

var Amount : Double
var Payer : String
var Description : String



init (amount: Double, payer: String, description: String){
    self.Amount = amount
    self.Payer = payer
    self.Description = description

    super.init()

}

required convenience init(coder decoder: NSCoder){
    let amount = decoder.decodeDoubleForKey("amount")
    let payer = decoder.decodeObjectForKey("payer") as! String
    let description = decoder.decodeObjectForKey("description") as! String
    self.init(amount: amount,payer: payer,description: description)
}
func encodeWithCoder(aCoder: NSCoder) {
    aCoder.encodeDouble(self.Amount, forKey: "amount")
    aCoder.encodeObject(self.Payer, forKey: "payer")
    aCoder.encodeObject(self.Description, forKey: "description")
}


}

And I implemented my retrieve function in the viewWillAppear method like this:

Debts = RetrieveArray("Debts", array: Debts)

But for some unknown reason, when I run a playground test like the one below, it works just fine:

var IOUArray : [IOU] = [IOU]()


var example = IOU(amount: 70, payer: "Jackson", description: "Because")
IOUArray.append(example)


func SaveArray (array: [IOU],fileID: String){
    NSKeyedArchiver.archiveRootObject(array, toFile: fileID)
}
func RetrieveArray (fileID: String) -> [IOU]{
    let IOUA = NSKeyedUnarchiver.unarchiveObjectWithFile(fileID) as! [IOU]
    return IOUA
}

SaveArray(IOUArray, fileID: "IOUArray")
RetrieveArray("IOUArray")
print(RetrieveArray("IOUArray")[0].Amount)

Answer 1

The value of the parameter toFile in the method archiveRootObject and the parameter in unarchiveObjectWithFile must be a valid file path..

archiveRootObject returns true if the operation was successful, otherwise false