ios - Save and retrieve value via KeyChain

Question

I'm trying to store an Integer and retrieve it using KeyChain.

This is how I save it:

func SaveNumberOfImagesTaken()
    {
        let key = "IMAGE_TAKEN"
        var taken = 10
        let data = NSKeyedArchiver.archivedDataWithRootObject(taken)
        let query : [String:AnyObject] = [
            kSecClass as String : kSecClassGenericPassword,
            kSecAttrAccount as String : key,
            kSecValueData as String : data
        ]
        let status : OSStatus = SecItemAdd(query as CFDictionaryRef, nil)

    }

This is how I try to retrieve it:

func CheckIfKeyChainValueExitss() -> AnyObject? {
    var key = "IMAGE_TAKEN"
    let query : [String:AnyObject] = [
        kSecClass as String       : kSecClassGenericPassword,
        kSecAttrAccount as String : key,
        kSecReturnData as String  : kCFBooleanTrue,
        kSecMatchLimit as String  : kSecMatchLimitOne ]

    var dataTypeRef :Unmanaged<AnyObject>?

    let status: OSStatus = SecItemCopyMatching(query, &dataTypeRef)

    if let op = dataTypeRef?.toOpaque() {
        let data = Unmanaged<NSData>.fromOpaque(op).takeUnretainedValue()
        if let string: AnyObject? =  NSKeyedUnarchiver.unarchiveObjectWithData(data) as? AnyObject? {
            if key == "IMAGE_TAKEN"
            {
                return string as! String!

            }
            else if string == nil
            {
                return nil
            }
        }
    }
    return nil

}

I'm getting the following error:

Could not cast value of type '__NSCFNumber' to 'NSString'

I tried playing with the variables but without success.

Answer 1

I've update Eric's version for Swift 5:

class KeyChain {

    class func save(key: String, data: Data) -> OSStatus {
        let query = [
            kSecClass as String       : kSecClassGenericPassword as String,
            kSecAttrAccount as String : key,
            kSecValueData as String   : data ] as [String : Any]

        SecItemDelete(query as CFDictionary)

        return SecItemAdd(query as CFDictionary, nil)
    }

    class func load(key: String) -> Data? {
        let query = [
            kSecClass as String       : kSecClassGenericPassword,
            kSecAttrAccount as String : key,
            kSecReturnData as String  : kCFBooleanTrue!,
            kSecMatchLimit as String  : kSecMatchLimitOne ] as [String : Any]

        var dataTypeRef: AnyObject? = nil

        let status: OSStatus = SecItemCopyMatching(query as CFDictionary, &dataTypeRef)

        if status == noErr {
            return dataTypeRef as! Data?
        } else {
            return nil
        }
    }

    class func createUniqueID() -> String {
        let uuid: CFUUID = CFUUIDCreate(nil)
        let cfStr: CFString = CFUUIDCreateString(nil, uuid)

        let swiftString: String = cfStr as String
        return swiftString
    }
}

extension Data {

    init<T>(from value: T) {
        var value = value
        self.init(buffer: UnsafeBufferPointer(start: &value, count: 1))
    }

    func to<T>(type: T.Type) -> T {
        return self.withUnsafeBytes { $0.load(as: T.self) }
    }
}

---

I've update Eric's version for Swift 3:

class KeyChain {

    class func save(key: String, data: Data) -> OSStatus {
        let query = [
            kSecClass as String       : kSecClassGenericPassword as String,
            kSecAttrAccount as String : key,
            kSecValueData as String   : data ] as [String : Any]

        SecItemDelete(query as CFDictionary)

        return SecItemAdd(query as CFDictionary, nil)
    }

    class func load(key: String) -> Data? {
        let query = [
            kSecClass as String       : kSecClassGenericPassword,
            kSecAttrAccount as String : key,
            kSecReturnData as String  : kCFBooleanTrue,
            kSecMatchLimit as String  : kSecMatchLimitOne ] as [String : Any]

        var dataTypeRef: AnyObject? = nil

        let status: OSStatus = SecItemCopyMatching(query as CFDictionary, &dataTypeRef)

        if status == noErr {
            return dataTypeRef as! Data?
        } else {
            return nil
        }
    }

    class func createUniqueID() -> String {
        let uuid: CFUUID = CFUUIDCreate(nil)
        let cfStr: CFString = CFUUIDCreateString(nil, uuid)

        let swiftString: String = cfStr as String
        return swiftString
    }
}

extension Data {

    init<T>(from value: T) {
        var value = value
        self.init(buffer: UnsafeBufferPointer(start: &value, count: 1))
    }

    func to<T>(type: T.Type) -> T {
        return self.withUnsafeBytes { $0.pointee }
    }
}

Example usage:

let int: Int = 555
let data = Data(from: int)
let status = KeyChain.save(key: "MyNumber", data: data)
print("status: ", status)

if let receivedData = KeyChain.load(key: "MyNumber") {
    let result = receivedData.to(type: Int.self)
    print("result: ", result)
}