在继承至 UITabBarController的类中隐藏tabB

func setTabBarVisible(visible:Bool,animated:Bool) {
        if (tabBarIsVisible() == visible) { return }
        let frame = tabBar.frame
        let offsetY = (visible ? -49.0 : 49.0)
        
        let duration:TimeInterval = (animated ? 0.3 : 0.0)
        if frame != nil {
            UIView.animate(withDuration: duration) {
                self.tabBar.frame = frame.offsetBy(dx: 0, dy: CGFloat(offsetY))
                return
            }
        }
    }
    
    func tabBarIsVisible() -> Bool{
        let tabbarY = tabBar.frame.origin.y
        print("tabbarY = \(tabbarY)")
        return tabbarY < self.view.frame.maxY //self.view.frame.maxY
    }