记录一些iOS里方便的扩展方法

iOS+Extension.swift

// MARK: UIViewController
extension UIViewController {
    static var topMost: UIViewController? {
        var top = UIApplication.shared.keyWindow?.rootViewController
        while true {
            if let presented = top?.presentedViewController {
                top = presented
            } else if let nav = top as? UINavigationController {
                top = nav.visibleViewController
            } else if let tab = top as? UITabBarController {
                top = tab.selectedViewController
            } else {
                break
            }
        }
        return top
    }
}