I wonder how I can change the font and size of title in my tabs when I use tab bar.
I have looked in the docs and I cant find anything about title font and size - source
You can change it via the appearance proxy:
let font: UIFont = ... UITabBarItem.appearance().setTitleTextAttributes([NSFontAttributeName: font], forState: .Normal)
You should put this in your app delegate in
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool