ios - 保存 CKRecord 时的错误处理

Question

我正在寻找保存 CKRecord 时正确处理错误的示例。根据Apple docs我应该“使用错误对象中的信息来确定问题是否有解决方法。”

我知道错误对象有一个 userInfo 字典，但我如何找出字典的键以及如何处理错误？

以下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);
    }

}];

如何改进此代码以解决潜在的保存问题？

Answer 1

在我的图书馆EVCloudKitDao我有一个单独的方法，它将根据错误代码返回错误类型。根据该类型，您可以决定要做什么。这是该方法:

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
            }
    })
}

在我上面的例子中，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。先检查是否有错误。