Make part of a UILabel bold in Swift

You will want to use attributedString which allows you to style parts of a string etc. This can be done like this by having two styles, one normal, one bold, and then attaching them together:

let boldText = "Filter:"
let attrs = [NSAttributedString.Key.font : UIFont.boldSystemFont(ofSize: 15)]
let attributedString = NSMutableAttributedString(string:boldText, attributes:attrs)

let normalText = "Hi am normal"
let normalString = NSMutableAttributedString(string:normalText)

attributedString.append(normalString)

When you want to assign it to a label:

label.attributedText = attributedString