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我的应用程序设置为接收 CloudKit 远程通知。有时它在后台运行时会收到这些通知。我还没有对这些通知做任何事情——我只是将 UIBackgroundFetchResultNewData 传递给了完成处理程序。原因是我不认为我可以在后台简单地从 CloudKit 下载 - 我认为只能通过 Background Fetch 或设置一个在后台运行的特殊作业来完成。但我现在正在重新审视这一点，我发现在 UIApplicationStateBackground 中运行 CKFetchRecordsOperation 并下载相关的 CKAsset 文件似乎确实有效。

所以我目前的代码是这样的：

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {

    __ENTERING_METHOD__
    CKNotification *ckNotification = [CKNotification notificationFromRemoteNotificationDictionary:userInfo];
    if (ckNotification) {
        if ([ckNotification.subscriptionID isEqualToString:kCKDocumentChangeSubscription]) {
            CKRecordID *recordID = [(CKQueryNotification*)ckNotification recordID];
            if (recordID) {
                if([UIApplication sharedApplication].applicationState == UIApplicationStateBackground) {

                    if (completionHandler) {
                        completionHandler(UIBackgroundFetchResultNewData);
                    }
                }
                else {
                    CKFetchRecordsOperation *fetchRecordsOperation = [[CKFetchRecordsOperation alloc] initWithRecordIDs:@[recordID]];
                    fetchRecordsOperation.fetchRecordsCompletionBlock = ^(NSDictionary *recordsByRecordID, NSError *error) {

                        if (error) {
                            dispatch_async(dispatch_get_main_queue(), ^{
                                if (completionHandler) {
                                    completionHandler(UIBackgroundFetchResultFailed);
                                }
                            });
                        }
                        else {
                            CKRecord *ckDocumentRecord = recordsByRecordID[recordID];
                            CKAsset *documentAsset = [ckDocumentRecord objectForKey:ckDocumentAsset];
                            NSData *data = [NSData dataWithContentsOfURL:documentAsset.fileURL];
                            [self handleData:data];

                            UIBackgroundFetchResult result = (data == nil)?UIBackgroundFetchResultFailed:UIBackgroundFetchResultNewData;
                            if (completion) {
                                completion(result);
                            }
                        }

                    };
                    CKContainer *defaultContainer = [CKContainer defaultContainer];
                    CKDatabase *publicDatabase = [defaultContainer publicCloudDatabase];
                    [publicDatabase addOperation:fetchRecordsOperation];
                }
            }
            else {
                if (completionHandler) {
                    completionHandler(UIBackgroundFetchResultFailed);
                }
            }
        }
        else {
            if (completionHandler) {
                completionHandler(UIBackgroundFetchResultNoData);
            }
        }
    }
    else {
        if (completionHandler) {
            completionHandler(UIBackgroundFetchResultNoData);
        }
    }
}

我希望这段代码是这样的：

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {

    __ENTERING_METHOD__
    CKNotification *ckNotification = [CKNotification notificationFromRemoteNotificationDictionary:userInfo];
    if (ckNotification) {
        if ([ckNotification.subscriptionID isEqualToString:kCKDocumentChangeSubscription]) {
            CKRecordID *recordID = [(CKQueryNotification*)ckNotification recordID];
            if (recordID) {
                CKFetchRecordsOperation *fetchRecordsOperation = [[CKFetchRecordsOperation alloc] initWithRecordIDs:@[recordID]];
                fetchRecordsOperation.fetchRecordsCompletionBlock = ^(NSDictionary *recordsByRecordID, NSError *error) {

                    if (error) {
                        dispatch_async(dispatch_get_main_queue(), ^{
                            if (completionHandler) {
                                completionHandler(UIBackgroundFetchResultFailed);
                            }
                        });
                    }
                    else {
                        CKRecord *ckDocumentRecord = recordsByRecordID[recordID];
                        CKAsset *documentAsset = [ckDocumentRecord objectForKey:ckDocumentAsset];
                        NSData *data = [NSData dataWithContentsOfURL:documentAsset.fileURL];
                        [self handleData:data];

                        UIBackgroundFetchResult result = (data == nil)?UIBackgroundFetchResultFailed:UIBackgroundFetchResultNewData;
                        if (completion) {
                            completion(result);
                        }
                    }

                };
                CKContainer *defaultContainer = [CKContainer defaultContainer];
                CKDatabase *publicDatabase = [defaultContainer publicCloudDatabase];
                [publicDatabase addOperation:fetchRecordsOperation];
            }
            else {
                if (completionHandler) {
                    completionHandler(UIBackgroundFetchResultFailed);
                }
            }
        }
        else {
            if (completionHandler) {
                completionHandler(UIBackgroundFetchResultNoData);
            }
        }
    }
    else {
        if (completionHandler) {
            completionHandler(UIBackgroundFetchResultNoData);
        }
    }
}

在后台运行 CKFetchRecordsOperation 并下载相关的 CKAsset 文件是否构成违反可以（或应该）在后台执行的操作？

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