How to encode an array of CGPoints with NSCoder in Swift? - arrays

Question

I am trying to save a copy of my custom class to a file, my class has 2 arrays of CGPoints which I append to every so often, they look like this:
class BlockAttributes: NSObject {
var positions:[CGPoint] = []
var spawns:[CGPoint] = []
}
Everything is working great as far as just as using and accessing the class goes, but archiving it does not work. I can archive arrays of Strings, Bools, and Ints just fine in my other classes but my game fails every time I try to use NSCoder to encode my arrays of CGPoints. Here is my code for archiving:
func encodeWithCoder(coder: NSCoder!) {
coder.encodeObject(positions, forKey: "positions")
coder.encodeObject(spawns, forKey: "spawns")
}
....
class ArchiveData: NSObject {
var documentDirectories:NSArray = []
var documentDirectory:String = ""
var path:String = ""
func saveData(data: BlockAttributes) {
documentDirectories = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
documentDirectory = documentDirectories.objectAtIndex(0) as! String
path = documentDirectory.stringByAppendingPathComponent("data.archive")
if NSKeyedArchiver.archiveRootObject(data, toFile: path) {
print("Success writing to file!")
} else {
print("Unable to write to file!")
}
}
func retrieveData() -> NSObject {
var dataToRetrieve = BlockAttributes()
documentDirectories = NSSearchPathForDirectoriesInDomains(.DocumentDirectory, .UserDomainMask, true)
documentDirectory = documentDirectories.objectAtIndex(0) as! String
path = documentDirectory.stringByAppendingPathComponent("data.archive")
if let dataToRetrieve2 = NSKeyedUnarchiver.unarchiveObjectWithFile(path) as? BlockAttributes {
dataToRetrieve = dataToRetrieve2 as BlockAttributes
}
return(dataToRetrieve)
}
}
....
And to save:
let archiveData = ArchiveData()
archiveData.saveData(myBlockActionsObject)
I even tried creating my own custom class to save the CGPoints to, which I call MyCGPoint (I read somewhere on SO that creating custom classes for some data types resolves some NSCoder issues):
class MyCGPoint: NSObject {
var x: CGFloat = 0.0
var y: CGFloat = 0.0
init(X: CGFloat, Y: CGFloat) {
x = X
y = Y
}
override init() {
}
}
....
class BlockAttributes: NSObject {
var positions:[MyCGPoint] = []
var spawns:[MyCGPoint] = []
}
But alas, I am still getting this error:
[Game.MyCGPoint encodeWithCoder:]:
unrecognized selector sent to instance 0x137f1d1a0 Game[20953:5814436]
*** Terminating app due to uncaught exception 'NSInvalidArgumentException',
reason: '-[Game.MyCGPoint encodeWithCoder:]:
unrecognized selector sent to instance 0x137f1d1a0'
Any idea how I can use encodeObject to encode my array of CGPoints/MyCGPoints?

Answer 1

You can convert them to and from strings:
//To string
let point = CGPointMake(0, 0)
let string = NSStringFromCGPoint(point)
//Or if you want String instead of NSString
let string = String(point)
//From string
let point2 = CGPointFromString(string)

Answer 2

CGPoint (and its Cocoa's twin NSPoint) are structs, i.e. value type, so you can't encode them directly. Wrap them in NSValue:
let positionValues = positions.map { NSValue(point:$0) }
let spawnValues = spawns.map { NSValue(point:$0) }
coder.encodeObject(positionValues, forKey: "positions")
coder.encodeObject(spawnValues, forKey: "spawns")
// Decode:
positons = (coder.decodeObjectForKey("positions") as! [NSValue]).map { $0.pointValue }
spawns = (coder.decodeObjectForKey("spawns") as! [NSValue]).map { $0.pointValue }
When you write your custom wrapper class, you have to make it compliant with NSCoding too, which NSValeu had already done for you, for free.