swift - 从仅解包选项中向下转换；您是要使用 '!' 吗？

Question

我有这个奇怪的错误，不知道如何修复它。

guard let theDialogObjects = dialogObjects as! [QBChatDialog]

Downcast from '[QBChatDialog]?' to '[QBChatDialog]' only unwraps optionals; did you mean to use '!'?

代码来自这里:https://github.com/QuickBlox/q-municate-services-ios/blob/master/QMChatService/QMChatService/QMChatService.m

- (void)allDialogsWithPageLimit:(NSUInteger)limit
                extendedRequest:(NSDictionary *)extendedRequest
                 iterationBlock:(void(^)(QBResponse *response, NSArray *dialogObjects, NSSet *dialogsUsersIDs, BOOL *stop))iterationBlock
                     completion:(void(^)(QBResponse *response))completion {

这是我在 Swift 中使用它的方式:

QMServicesManager.instance().chatService.allDialogsWithPageLimit(UInt.max, extendedRequest: ["type":String(QBChatDialogType.Private.rawValue)], iterationBlock: { (response, dialogObjects, userIDs, stop) in

      guard let theDialogObjects = dialogObjects as! [QBChatDialog]{
        return
      }

Answer 1

从错误消息中您并没有尝试更改类型，只是检查值不为 nil，因此您的检查应该是:

guard let theDialogObjects = dialogObjects else ...