ios nsattributedstring swift swift4 uilabel

Swift 4 Label attributes

I’m moving from swift 3 to swift 4. I have UILabels that I am giving very specific text properties to the label. I’m getting an ‘unexpectedly found nil while unwrapping optional value’ error when strokeTextAttributes is being initialized. I’m totally lost to be frank.

In swift 3 the of strokeTextAttributes was [String : Any] but swift 4 threw errors until I changed it to what it is below.

let strokeTextAttributes = [
NSAttributedStringKey.strokeColor.rawValue :,
NSAttributedStringKey.foregroundColor : UIColor.white,
NSAttributedStringKey.strokeWidth : -2.0,
NSAttributedStringKey.font : UIFont.boldSystemFont(ofSize: 18)
] as! [NSAttributedStringKey : Any]
chevronRightLabel.attributedText = NSMutableAttributedString(string: "0", attributes: strokeTextAttributes)