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How to use Dynamic Type to resize your app's text

Swift version: 5.1

Paul Hudson    @twostraws   

Ever since iOS 7.0 users can set a system-wide preferred font size for all apps, but many programmers ignore this setting much to user's annoyance. You're not one of those developers, are you? Of course not! So here's how to honor a user's font settings using UIFont:

let headlineFont = UIFont.preferredFont(forTextStyle: .headline)
let subheadFont = UIFont.preferredFont(forTextStyle: .subheadline)

And that's it! This technology is called Dynamic Type, and it's powerful because that code will return correctly sized fonts for the user's preference, which means your app's text will shrink or grow as needed.

Note that it is technically possible for users to change their Dynamic Type setting while your app is running. If you want to cover this corner case, use NotificationCenter to subscribe to the UIContentSizeCategoryDidChange notification then refresh your user interface if you receive it.

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