Changing specific text’s color using NSMutableAttributedString in Swift

let mainString = "Hello World"
let stringToColor = "World"

SWIFT 5

let range = (mainString as NSString).range(of: stringToColor)

let mutableAttributedString = NSMutableAttributedString.init(string: mainString)
mutableAttributedString.addAttribute(NSAttributedString.Key.foregroundColor, value: UIColor.red, range: range)

textField = UITextField.init(frame: CGRect(x:10, y:20, width:100, height: 100))
textField.attributedText = mutableAttributedString

SWIFT 4.2

let range = (mainString as NSString).range(of: stringToColor)
    

let mutableAttributedString = NSMutableAttributedString.init(string: mainString)
mutableAttributedString.addAttribute(NSAttributedStringKey.foregroundColor, value: UIColor.red, range: range)     
    
textField = UITextField.init(frame: CGRect(x:10, y:20, width:100, height: 100))
textField.attributedText = mutableAttributedString