Swift 4 Label attributes

In Swift 4.0+, attributed string accepts json (dictionary) with key type NSAttributedStringKey or NSAttributedString.Key.

So you must change it from [String : Any] to

Swift 4.1 & below - [NSAttributedStringKey : Any] &
Swift 4.2 & above - [NSAttributedString.Key : Any]

Swift 4.2

Initialiser for AttributedString in Swift 4.2 is changed to [NSAttributedString.Key : Any]?

public init(string str: String, attributes attrs: [NSAttributedString.Key : Any]? = nil)

Here is sample working code.

let label = UILabel()
let labelText = "String Text"

let strokeTextAttributes = [
     NSAttributedString.Key.strokeColor : UIColor.black,
     NSAttributedString.Key.foregroundColor : UIColor.white,
     NSAttributedString.Key.strokeWidth : -2.0,
     NSAttributedString.Key.font : UIFont.boldSystemFont(ofSize: 18)
   ] as [NSAttributedString.Key : Any]

label.attributedText = NSAttributedString(string: labelText, attributes: strokeTextAttributes)

Swift 4.0

Initialiser for AttributedString in Swift 4.0 is changed to [NSAttributedStringKey : Any]?.

public init(string str: String, attributes attrs: [NSAttributedStringKey : Any]? = nil)

Here is sample working code.

let label = UILabel()
let labelText = "String Text"

let strokeTextAttributes = [
     NSAttributedStringKey.strokeColor : UIColor.black,
     NSAttributedStringKey.foregroundColor : UIColor.white,
     NSAttributedStringKey.strokeWidth : -2.0,
     NSAttributedStringKey.font : UIFont.boldSystemFont(ofSize: 18)
   ] as [NSAttributedStringKey : Any]

label.attributedText = NSAttributedString(string: labelText, attributes: strokeTextAttributes)

Look at this Apple Document, for more info: NSAttributedString - Creating an NSAttributedString Object

@Larme's comment about the .rawValue not being needed is correct.

Also, you can avoid the force cast that crashes your code using explicit typing:

let strokeTextAttributes: [NSAttributedString.Key: Any] = [
    .strokeColor : UIColor.black,
    .foregroundColor : UIColor.white,
    .strokeWidth : -2.0,
    .font : UIFont.boldSystemFont(ofSize: 18)
]

This gets rid of the repetitive NSAttributedString.Key., too.

NSAttributedStringKey.strokeColor.rawValue is of type String

NSAttributedStringKey.strokeColor is of type NSAttributedStringKey

So its unable to convert String to NSAttributedStringKey . You have to use like below:

let strokeTextAttributes: [NSAttributedStringKey : Any] = [
    NSAttributedStringKey.strokeColor : UIColor.black,
    NSAttributedStringKey.foregroundColor : UIColor.white,
    NSAttributedStringKey.strokeWidth : -2.0,
    NSAttributedStringKey.font : UIFont.boldSystemFont(ofSize: 18)
]