如果是root就可以了

You can do this if it's the root

if let vc = self.window?.rootViewController as? ViewController {
    vc.result.text = u
}

要获得完整的解决方案，您应该使用 获得最***的 UIViewController 获得最***的 vc，然后像上面一样投射

For a complete solution you should get the top most vc with Get top most UIViewController then cast it like above