App开发Xcode报错 UIModalPresentationPopover 在iPad上

App开发Xcode报错The modalPresentationStyle of a UIAlertController with this style is UIModalPresentationPopover在iPad上

解决方法如下，添加如下代码

if let popoverController = alertController.popoverPresentationController {
popoverController.barButtonItem = navigationItem.rightBarButtonItem
}

其他方法

Swift 5
var alertStyle = UIAlertController.Style.actionSheet
if (UIDevice.current.userInterfaceIdiom == .pad) {
alertStyle = UIAlertController.Style.alert
}

let alertController = UIAlertController(title: "Your title", message: nil, preferredStyle: alertStyle)

Swift4
extension UIViewController {
public func addActionSheetForiPad(actionSheet: UIAlertController) {
if let popoverPresentationController = actionSheet.popoverPresentationController {
popoverPresentationController.sourceView = self.view
popoverPresentationController.sourceRect = CGRect(x: self.view.bounds.midX, y: self.view.bounds.midY, width: 0, height: 0)
popoverPresentationController.permittedArrowDirections = []
}
}
}
How to use:

let actionSheetVC = UIAlertController(title: "Title", message: nil, preferredStyle: .actionSheet)
addActionSheetForIpad(actionSheet: actionSheetVC)
present(actionSheetVC, animated: true, completion: nil)