Converting Swift Array to NSData for NSUserDefaults.StandardUserDefaults persistent storage

Question

I\'m trying to get my head around Swift (after being relatively competent with Obj-C) by making a small app. I would like to use NSUserDefaults to persistently save a small

Answer 1

Anything you are archiving to NSData and back needs to implement the NSCoding protocol. I found that in addition, my Swift class had to extend NSObject. Here is a quick example of a Swift class that encodes and decodes:

class B : NSObject, NSCoding {
    var str : String = "test"

    required init(coder aDecoder: NSCoder) {
        str = aDecoder.decodeObjectForKey("str") as String
    }

    override init() {
    }

    func encodeWithCoder(aCoder: NSCoder) {
        aCoder.encodeObject(str, forKey: "str")
    }
}

// create an Object of Class B
var b : B = B()

// Archive it to NSData
var data : NSData = NSKeyedArchiver.archivedDataWithRootObject(b)

// Create a new object of Class B from the data
var b2 : B = NSKeyedUnarchiver.unarchiveObjectWithData(data) as B