protocol KeyPathBasedBinding {}
extension KeyPathBasedBinding
{
    /// When the returned object is deinited or invalidated, it will stop binding.
    /// - Parameter targetKeyPath: The KeyPath for target property. Target property must be observable through KVO.
    func bind<Value, Target>(_ keyPath: ReferenceWritableKeyPath<Self, Value>, to targetKeyPath: KeyPath<Target, Value>, of target: Target) -> NSKeyValueObservation where Self: AnyObject, Target: _KeyValueCodingAndObserving
    {
        return target.observe(targetKeyPath, options: [.initial, .new], changeHandler: { [weak self] (sender, change) in
            self?[keyPath: keyPath] = target[keyPath: targetKeyPath]
        })
    }

    /// When the returned object is deinited or invalidated, it will stop binding.
    /// - Parameter targetKeyPath: The KeyPath for target property. Target property must be observable through KVO.
    func bind<Value, Target>(_ keyPath: ReferenceWritableKeyPath<Self, Value>, to targetKeyPath: KeyPath<Target, Optional<Value>>, of target: Target, nullValue: Value) -> NSKeyValueObservation where Self: AnyObject, Target: _KeyValueCodingAndObserving
    {
        return target.observe(targetKeyPath, options: [.initial, .new], changeHandler: { [weak self] (sender, change) in
            self?[keyPath: keyPath] = (target[keyPath: targetKeyPath] ?? nullValue)
        })
    }
}
extension NSObject: KeyPathBasedBinding {}

enum MyKey: String
{
    case identifier
    case colorCode
}

func process(_ dictionary: [String: Any])
{
    let identifier = dictionary[MyKey.identifier.rawValue] as? String
    let colorCode = dictionary[MyKey.colorCode.rawValue] as? Int
    ...
}

extension Dictionary
{
    subscript<WrappedKey: RawRepresentable>(_ key: WrappedKey) -> Value? where WrappedKey.RawValue == Key
    {
        get { return self[key.rawValue] }
        set { self[key.rawValue] = newValue }
    }
}

let identifier = dictionary[MyKey.identifier] as? String
let colorCode = dictionary[MyKey.colorCode] as? Int