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

Swift 2.1-3.0 code based on @smartDonkey's port of @Bob Spryn code. Also updated with the Apple sizes from @Klaas.

import UIKit

extension UIFontDescriptor {

    private struct SubStruct {
        static var preferredFontName: String = "Roboto-Light"
    }

    class func preferredDescriptor(textStyle: NSString) -> UIFontDescriptor {
        struct Static {
            static var onceToken : dispatch_once_t = 0
            static var fontSizeTable : NSDictionary = NSDictionary()
        }

        dispatch_once(&Static.onceToken) {
            Static.fontSizeTable = [
                UIFontTextStyleHeadline: [
                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: 23,
                    UIContentSizeCategoryAccessibilityExtraExtraLarge: 23,
                    UIContentSizeCategoryAccessibilityExtraLarge: 23,
                    UIContentSizeCategoryAccessibilityLarge: 23,
                    UIContentSizeCategoryAccessibilityMedium: 23,
                    UIContentSizeCategoryExtraExtraExtraLarge: 23,
                    UIContentSizeCategoryExtraExtraLarge: 21,
                    UIContentSizeCategoryExtraLarge: 19,
                    UIContentSizeCategoryLarge: 17,
                    UIContentSizeCategoryMedium: 16,
                    UIContentSizeCategorySmall: 15,
                    UIContentSizeCategoryExtraSmall: 14
                ],
                UIFontTextStyleSubheadline: [
                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: 21,
                    UIContentSizeCategoryAccessibilityExtraExtraLarge: 21,
                    UIContentSizeCategoryAccessibilityExtraLarge: 21,
                    UIContentSizeCategoryAccessibilityLarge: 21,
                    UIContentSizeCategoryAccessibilityMedium: 21,
                    UIContentSizeCategoryExtraExtraExtraLarge: 21,
                    UIContentSizeCategoryExtraExtraLarge: 19,
                    UIContentSizeCategoryExtraLarge: 17,
                    UIContentSizeCategoryLarge: 15,
                    UIContentSizeCategoryMedium: 14,
                    UIContentSizeCategorySmall: 13,
                    UIContentSizeCategoryExtraSmall: 12
                ],
                UIFontTextStyleBody: [
                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: 53,
                    UIContentSizeCategoryAccessibilityExtraExtraLarge: 47,
                    UIContentSizeCategoryAccessibilityExtraLarge: 40,
                    UIContentSizeCategoryAccessibilityLarge: 33,
                    UIContentSizeCategoryAccessibilityMedium: 28,
                    UIContentSizeCategoryExtraExtraExtraLarge: 23,
                    UIContentSizeCategoryExtraExtraLarge: 21,
                    UIContentSizeCategoryExtraLarge: 19,
                    UIContentSizeCategoryLarge: 17,
                    UIContentSizeCategoryMedium: 16,
                    UIContentSizeCategorySmall: 15,
                    UIContentSizeCategoryExtraSmall: 14
                ],
                UIFontTextStyleCaption1: [
                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: 18,
                    UIContentSizeCategoryAccessibilityExtraExtraLarge: 18,
                    UIContentSizeCategoryAccessibilityExtraLarge: 18,
                    UIContentSizeCategoryAccessibilityLarge: 18,
                    UIContentSizeCategoryAccessibilityMedium: 18,
                    UIContentSizeCategoryExtraExtraExtraLarge: 18,
                    UIContentSizeCategoryExtraExtraLarge: 16,
                    UIContentSizeCategoryExtraLarge: 14,
                    UIContentSizeCategoryLarge: 12,
                    UIContentSizeCategoryMedium: 11,
                    UIContentSizeCategorySmall: 11,
                    UIContentSizeCategoryExtraSmall: 11
                ],
                UIFontTextStyleCaption2: [
                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: 17,
                    UIContentSizeCategoryAccessibilityExtraExtraLarge: 17,
                    UIContentSizeCategoryAccessibilityExtraLarge: 17,
                    UIContentSizeCategoryAccessibilityLarge: 17,
                    UIContentSizeCategoryAccessibilityMedium: 17,
                    UIContentSizeCategoryExtraExtraExtraLarge: 17,
                    UIContentSizeCategoryExtraExtraLarge: 15,
                    UIContentSizeCategoryExtraLarge: 13,
                    UIContentSizeCategoryLarge: 11,
                    UIContentSizeCategoryMedium: 11,
                    UIContentSizeCategorySmall: 11,
                    UIContentSizeCategoryExtraSmall: 11
                ],
                UIFontTextStyleFootnote: [
                    UIContentSizeCategoryAccessibilityExtraExtraExtraLarge: 19,
                    UIContentSizeCategoryAccessibilityExtraExtraLarge: 19,
                    UIContentSizeCategoryAccessibilityExtraLarge: 19,
                    UIContentSizeCategoryAccessibilityLarge: 19,
                    UIContentSizeCategoryAccessibilityMedium: 19,
                    UIContentSizeCategoryExtraExtraExtraLarge: 19,
                    UIContentSizeCategoryExtraExtraLarge: 17,
                    UIContentSizeCategoryExtraLarge: 15,
                    UIContentSizeCategoryLarge: 13,
                    UIContentSizeCategoryMedium: 12,
                    UIContentSizeCategorySmall: 12,
                    UIContentSizeCategoryExtraSmall: 12
                ],
            ]
        }

        let contentSize = UIApplication.sharedApplication().preferredContentSizeCategory
        let style = Static.fontSizeTable[textStyle] as! NSDictionary
        return UIFontDescriptor(name: SubStruct.preferredFontName, size: CGFloat((style[contentSize] as! NSNumber).floatValue))
    }

}