How to use a custom font with dynamic text sizes in iOS7

Question

In iOS7 there are new API\'s for getting a font that is automatically adjusted to the text size the user has set in their preferences.

It looks something like this to

Answer 1

In iOS 11 you can use:

var customFont = UIFont.systemFont(ofSize: 17.0)
if #available(iOS 11.0, *) {
    customFont = UIFontMetrics.default.scaledFont(for: customFont)
}
// use customFont...

See also Building Apps with Dynamic Type WWDC 2017 - Session 245 - iOS time 8:34.