How to encode a value passed through a delegate using NSCoding - ios

Question

I'm really new using the NSCoding functionality, I'm trying to create persistence of data of an attributedString, particularly a UIColor that is passed through a delegate. I haven't found a tutorial that encodes values that are not declared and initialized in the same class in which the NSCoding protocol is conformed.
I have the following code, which is the method that conforms to the protocol I created, and assigns the passed color value as an attribute to the attributedString.
func didSelectColorCell(color: UIColor) {
let coder = NSCoder.init()
color.encode(with: coder)
noteTextView.setAttributedValueAtSelectedTextRange(NSForegroundColorAttributeName, value: color)
}
The app crashes, and sends me a warning "cannot be sent to an abstract object of class NSCoder: Create a concrete instance!" I'm really lost on how to procede. I don't know how to adapt this tutorial http://nshipster.com/nscoding/ to my scenario.
Can someone please provide me guidance on how to order my ideas or how does NSCoding work with delegates? Any help would be appreciated :)

Answer 1

Define a class to implement the NSCoding protocol (Playground sample):
class ColorHelper: NSObject, NSCoding {
var color: UIColor?
init(color: UIColor) {
super.init()
self.color = color
}
required init(coder aDecoder: NSCoder) {
if let color = aDecoder.decodeObject(forKey: "color") as? UIColor {
self.color = color
}
}
func encode(with aCoder: NSCoder) {
aCoder.encode(color, forKey: "color")
}
func save(defaults key: String) -> Bool {
let defaults = UserDefaults.standard
let savedData = NSKeyedArchiver.archivedData(withRootObject: data)
defaults.set(savedData, forKey: key)
return defaults.synchronize()
}
convenience init?(defaults key: String) {
let defaults = UserDefaults.standard
if let data = defaults.object(forKey: key) as? Data,
let obj = NSKeyedUnarchiver.unarchiveObject(with: data) as? ColorHelper,
let color = obj.color {
self.init(color: color)
} else {
return nil
}
}
}
let data = ColorHelper(color: .red)
let savedData = NSKeyedArchiver.archivedData(withRootObject: data)
let obj = NSKeyedUnarchiver.unarchiveObject(with: savedData) as? ColorHelper
obj?.color
In your code:
func didSelectColorCell(color: UIColor) {
let helper = ColorHelper(color: color)
helper.save(defaults: "color")
noteTextView.setAttributedValueAtSelectedTextRange(NSForegroundColorAttributeName, value: color)
}
To read the saved data:
let color = ColorHelper(defaults: "color")?.color