iOS拖拽控件到代码区提示错误 Could not insert

拉outlet到代码区提示错误：
Could not insert new outlet connection: Could not find any information for the class named XXX

这是Xcode抽风啦。。。解决方法如下

在代码区手动写 @IBOutlet weak ...或@IBAction func ...，然后点代码左边圆圈反拖给storyboard上的控件
@IBOutlet weak var viewName: UIView!
// or
@IBAction func viewTapped(_ sender: Any) { }