Archiving swift objects

Archiver.swift

import Foundation

public protocol Archivable {
    
    typealias T
    
    static func decompress(object: AnyObject) -> T?
    static func compress(object: T) -> AnyObject
}

public class Archiver<T: Archivable>: NSObject, NSCoding {
    
    private let value: T.T?
    
    private init(_ _value: T.T) {
        value = _value
        super.init()
    }
    
    required public init?(coder aDecoder: NSCoder) {
        
        guard let decodedObject = aDecoder.decodeObject() else {
            value = nil
            super.init()
            return
        }
        
        guard let decompressed: T.T = T.decompress(decodedObject) else {
            value = nil
            super.init()
            return
        }
        
        value = decompressed
        super.init()
    }
    
    public func encodeWithCoder(aCoder: NSCoder) {
        
        guard let value = value else {
            return
        }
        
        aCoder.encodeObject(T.compress(value))
    }
    
    static public func archive(object: T.T, toFile path: String) {
        
        NSKeyedArchiver.archiveRootObject(Archiver(object), toFile: path)
    }
    
    static public func unarchive(objectWithFile path: String) -> T.T? {
        
        guard let unarchived = NSKeyedUnarchiver.unarchiveObjectWithFile(path) as? Archiver else {
            return nil
        }
        
        return unarchived.value
    }
}