保存CKRecord时的错误处理

Question

我正在寻找一个在保存CKRecord时正确处理错误的示例。根据Apple docs的说法，我应该“使用error对象中的信息来确定问题是否有解决方法”。

我知道error对象有一个userInfo字典，但是我如何确定字典的键是什么以及如何处理错误呢？

下面的示例说明了我当前如何保存CKRecord

    CKRecord *record = [[CKRecord alloc] initWithRecordType:@"MyRecordType"];
[record setValue:[NSNumber numberWithInt:99] forKey:@"myInt"];

[db saveRecord:record completionHandler:^(CKRecord *savedPlace, NSError *error) {
    // handle errors here
    if (savedPlace) {
        NSLog(@"save successful");
    }else{
        NSLog(@"save unsuccessful");
    }
    if (error) {
        NSLog(@"Error saving %@", error.localizedDescription);
    }

}];

我如何改进这段代码，以便为潜在的保存问题提供解决方案？

Answer 1

在我的库EVCloudKitDao中，我有一个单独的方法，它将根据错误代码返回错误类型。根据类型的不同，您可以决定要做什么。以下是该方法：

public enum HandleCloudKitErrorAs {
    case Success,
    Retry(afterSeconds:Double),
    RecoverableError,
    Fail
}

public static func handleCloudKitErrorAs(error:NSError?, retryAttempt:Double = 1) -> HandleCloudKitErrorAs {
    if error == nil {
        return .Success
    }
    let errorCode:CKErrorCode = CKErrorCode(rawValue: error!.code)!
    switch errorCode {
    case .NetworkUnavailable, .NetworkFailure, .ServiceUnavailable, .RequestRateLimited, .ZoneBusy, .ResultsTruncated:
        // Use an exponential retry delay which maxes out at half an hour.
        var seconds = Double(pow(2, Double(retryAttempt)))
        if seconds > 1800 {
            seconds = 1800
        }
        // Or if there is a retry delay specified in the error, then use that.
        if let userInfo = error?.userInfo {
            if let retry = userInfo[CKErrorRetryAfterKey] as? NSNumber {
                seconds = Double(retry)
            }
        }
        NSLog("Debug: Should retry in \(seconds) seconds. \(error)")
        return .Retry(afterSeconds: seconds)
    case .UnknownItem, .InvalidArguments, .IncompatibleVersion, .BadContainer, .MissingEntitlement, .PermissionFailure, .BadDatabase, .AssetFileNotFound, .OperationCancelled, .NotAuthenticated, .AssetFileModified, .BatchRequestFailed, .ZoneNotFound, .UserDeletedZone, .InternalError, .ServerRejectedRequest, .ConstraintViolation:
        NSLog("Error: \(error)")
        return .Fail;
    case .QuotaExceeded, .LimitExceeded:
        NSLog("Warning: \(error)")
        return .Fail;
    case .ChangeTokenExpired,  .ServerRecordChanged:
        NSLog("Info: \(error)")
        return .RecoverableError
    default:
        NSLog("Error: \(error)") //New error introduced in iOS...?
        return .Fail;
    }
}

在CloudKit方法的回调中，您可以像这样使用此函数：

func loadContacts(retryCount:Double = 1) {        
    // Look who of our contact is also using this app.
    EVCloudKitDao.publicDB.allContactsUserInfo({ users in
            EVLog("AllContactUserInfo count = \(users.count)");
            Async.main{
                self.contacts = users
                self.tableView.reloadData()
            }
        }, errorHandler: { error in
            switch EVCloudKitDao.handleCloudKitErrorAs(error, retryAttempt: retryCount) {
            case .Retry(let timeToWait):
                Async.background(after: timeToWait) {
                    self.loadContacts(retryCount + 1)
                }
            case .Fail:
                Helper.showError("Something went wrong: \(error.localizedDescription)")
            default: // For here there is no need to handle the .Success, .Fail and .RecoverableError
                break
            }
    })
}

在上面的例子中，我使用了一个单独的错误回调处理程序。您也可以在CloudKit方法回调中直接调用它。只需首先检查是否有错误。

Answer 2

下面是一个实现，在这个实现中，我通过在存储在userInfo字典中的建议重试时间间隔后重试保存来处理CKErrorNetworkFailure的常见错误。

-(void)saveRecord:(CKRecord*)record toDatabase:(CKDatabase*)database{
[database saveRecord:record completionHandler:^(CKRecord *record, NSError *error) {
    if (error==nil) {
        NSLog(@"The save was successful");
        //Do something
    }else{
        NSLog(@"Error saving with localizedDescription: %@", error.localizedDescription);
        NSLog(@"CKErrorCode = %lu", [error code]);

        if ([error code]==CKErrorNetworkFailure) {
            double retryAfterValue = [[error.userInfo valueForKey:CKErrorRetryAfterKey] doubleValue];
            NSLog(@"Error code network unavailable retrying after %f", retryAfterValue);
            NSTimer *timer = [NSTimer timerWithTimeInterval:retryAfterValue target:self selector:@selector(testOutCloudKit) userInfo:nil repeats:NO];
            [timer fire];
        }
    }
}];

}

Answer 3

在Swift 3中，我这样处理我的CloudKit错误：

privateDB.perform(myQuery, inZoneWith: nil)  {records, error in
    if error != nil {
        print (error?.localizedDescription)
        if error?._code == CKError.notAuthenticated.rawValue {
            // Solve problems here...
        }

请注意，在编写CKError之后，将从代码完成显示的列表中选择CKError.notAuthenticated。

希望这能有所帮助！