decode.swift

// This uses a legacy version of swift
import Foundation

class Model: NSObject, NSSecureCoding {
    let bar: String
    
    init(bar: String) {
        self.bar = bar
    }
    
    required init?(coder decoder: NSCoder) {
        // This is the problematic line mentioned in the error report
        // ** Amended note: passing [NSString.self] instead of Set(arrayLiteral: [NSString.self]) fixes this program's bug **
        self.bar = decoder.decodeObjectOfClasses(Set(arrayLiteral: [NSString.self]), forKey: "bar") as! String
        
        // This line would work fine, but not the line above which causes an exception to be raised
        //self.bar = decoder.decodeObjectOfClass(NSString.self, forKey: "bar") as! String
    }
    
    func encodeWithCoder(coder: NSCoder) {
        coder.encodeObject(self.bar, forKey: "bar")
    }
    
    static func supportsSecureCoding() -> Bool {
        return true
    }
}

print("Hello, World!")

let model = Model(bar: "meow")

// Encode some data
let encodedData = NSMutableData()
let keyedArchiver = NSKeyedArchiver(forWritingWithMutableData: encodedData)
keyedArchiver.requiresSecureCoding = true // make sure secure coding is enabled
keyedArchiver.encodeObject(model, forKey: "model")
keyedArchiver.finishEncoding()

// Decode data
let keyedUnarchiver = NSKeyedUnarchiver(forReadingWithData: encodedData)

// Make sure secure coding is enabled
// If this line is commented out, the program works properly but without secure validation...
keyedUnarchiver.requiresSecureCoding = true

// An exception on this line occurs, see below for the report..
let unarchivedTool = keyedUnarchiver.decodeObjectOfClass(Model.self, forKey: "model")!

keyedUnarchiver.finishDecoding()

// Test data
assert(unarchivedTool.bar == "meow")
print("YAY")

/*
 Hello, World!
 2016-10-18 16:43:12.269508 ArchiveTest[32621:1949468] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[NSKeyedUnarchiver decodeObjectOfClasses:forKey:] object in classes '(
 NSString
 )' is not an Objective-C class!'
 *** First throw call stack:
 (
	0   CoreFoundation                      0x00007fffa22b352b __exceptionPreprocess + 171
	1   libobjc.A.dylib                     0x00007fffb698bcad objc_exception_throw + 48
	2   CoreFoundation                      0x00007fffa2331a0d +[NSException raise:format:] + 205
	3   Foundation                          0x00007fffa3c2c6f4 -[NSKeyedUnarchiver decodeObjectOfClasses:forKey:] + 549
	4   ArchiveTest                         0x000000010002ac09 _TFE10FoundationCSo7NSCoder21decodeObjectOfClassesfTGSqCSo5NSSet_6forKeySS_GSqPs9AnyObject__ + 505
	5   ArchiveTest                         0x00000001000024b9 _TFC11ArchiveTest5ModelcfT5coderCSo7NSCoder_GSqS0__ + 377
	6   ArchiveTest                         0x000000010000260d _TToFC11ArchiveTest5ModelcfT5coderCSo7NSCoder_GSqS0__ + 45
	7
 libc++abi.dylib: terminating with uncaught exception of type NSException
 (lldb)
 */