UITabBarItem setTitleTextAttributes function declaration in Swift 4
open func setTitleTextAttributes(_ attributes: [NSAttributedStringKey : Any]?, for state: UIControlState)
So DesignableTabBarController, it need to change Attributes from String to NSAttributedStringKey
i.e.
change
UITabBarItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor.rawValue: normalTint], for: UIControlState())
to
UITabBarItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: normalTint], for: UIControlState())
So DesignableTabBarController, it need to change Attributes from String to NSAttributedStringKey i.e. change UITabBarItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor.rawValue: normalTint], for: UIControlState()) to UITabBarItem.appearance().setTitleTextAttributes([NSAttributedStringKey.foregroundColor: normalTint], for: UIControlState())