Custom font Swift

CustomFont.swift

import UIKit

extension UIFont {
    class func systemFontOfSize(size: CGFloat) -> UIFont {
        return UIFont(name: "CustomFont-Regular", size: size)!
    }
    func lightSystemFontOfSize(size: CGFloat) -> UIFont {
        return UIFont(name: "CustomFont-Light", size: size)!
    }
    func boldSystemFontOfSize(size: CGFloat) -> UIFont {
        return UIFont(name: "CustomFont-Bold", size: size)!
    }
    func preferredFontForTextStyle(style: String) -> UIFont {
        switch(style) {
        case UIFontTextStyleBody:
            return UIFont.systemFontOfSize(17)
        case UIFontTextStyleHeadline:
            return UIFont.boldSystemFontOfSize(17)
        case UIFontTextStyleSubheadline:
            return UIFont.systemFontOfSize(15)
        case UIFontTextStyleFootnote:
            return UIFont.systemFontOfSize(13)
        case UIFontTextStyleCaption1:
            return UIFont.systemFontOfSize(12)
        case UIFontTextStyleCaption2:
            return UIFont.systemFontOfSize(11)
        default:
            return UIFont.systemFontOfSize(17)
        }
    }
}