所以我试图为这样的视图控制器快速创建几个预览操作项:
@available(iOS 9.0, *)
override internal func previewActionItems() -> [UIPreviewActionItem] {
let cancelAction = UIPreviewAction(title: "Cancel Appointment", style: .Destructive) { (action, previewViewController) -> Void in
print("Cancel Appointment")
}
return [cancelAction]
}
这给了我这个编译错误消息:
Type of 'title' has different optionality than required by protocol 'UIPreviewActionItem'.
我理解错误消息,但我应该如何更改“标题”的可选性?
Objective-C 中的相同代码可以完美运行。