import Foundation

struct DictionaryWrapper<Key, Value> {

    private let getValue: (Key) -> Value?

    init(_ wrapped: NSDictionary) {
        getValue = { return wrapped[$0] as? Value }
    }

    subscript(key: Key) -> Value? {
        return getValue(key)
    }
}

struct TypedDictionaryWrapper {

    private let getValue: (String) -> Int?

    init(_ wrapped: NSDictionary) {
        getValue = { return wrapped[$0] as? Int }
    }

    subscript(key: String) -> Int? {
        return getValue(key)
    }
}

struct TypedDictionaryWrapper {
  private let getValue: (String) -> Any?

  init(_ wrapped: NSDictionary) {
    getValue = { return wrapped[$0] as? Any }
  }

  subscript(key: String) -> Any? {
    return getValue(key)
  }
}

// ...

class ViewController: UIViewController {

  override func viewDidLoad() {
    super.viewDidLoad()

    let dict = NSDictionary(dictionary: ["x": 10])
    let wrapper = DictionaryWrapper<String, Any>(dict)
    let value1 = wrapper["x"]
    print("Value: " + String(describing: value1))
    // in Swift 4, prints: "Value: Optional(10)"
    // in Swift 5, prints: "Value: Optional(Optional(10))"

    let typedWrapper = TypedDictionaryWrapper(dict)
    let value2 = typedWrapper["x"]
    print("Value: " + String(describing: value2))
    // in both versions, prints: "Value: Optional(Optional(10))"
  }
}