是什么导致DynamoDB UpdateItem在Swift中出现致命错误？ [英] What Causes DynamoDB UpdateItem to Giv Fatal Error in Swift?

问题描述

我正在使用Swift让我的应用程序更新DynamoDB上的项目。我按照示例 https://github.com /aws/aws-sdk-ios/blob/master/AWSiOSSDKTests/AWSDynamoDBTests.m#L244 ，即-（void）testUpdateItem方法。我的代码如下：

I am using Swift to let my app update an item on DynamoDB. I followed the example https://github.com/aws/aws-sdk-ios/blob/master/AWSiOSSDKTests/AWSDynamoDBTests.m#L244, the "- (void)testUpdateItem" method. My codes are as follows:

var dynamoDB = AWSDynamoDB()

var hashValue: AWSDynamoDBAttributeValue = AWSDynamoDBAttributeValue()
hashValue.S = userID
var updatedValue: AWSDynamoDBAttributeValue = AWSDynamoDBAttributeValue()
updatedValue.S = updatedContent

var updateInput: AWSDynamoDBUpdateItemInput = AWSDynamoDBUpdateItemInput()
updateInput.tableName = kAWSDynamoDBMoEndpointARNTableName
updateInput.key = ["UserID": hashValue]
var valueUpdate: AWSDynamoDBAttributeValueUpdate = AWSDynamoDBAttributeValueUpdate()
valueUpdate.value = updatedValue
valueUpdate.action = AWSDynamoDBAttributeAction.Put
updateInput.attributeUpdates = ["Updated": valueUpdate]
updateInput.returnValues = AWSDynamoDBReturnValue.UpdatedNew

dynamoDB.updateItem(updateInput).waitUntilFinished()

但是，当我运行代码时，它总是返回致命错误：意外发现nil同时展开一个可选值。调查错误，我发现它来自 Swift._fatalErrorMessage（Swift.StaticString，Swift.StaticString，Swift.StaticString，Swift.Uint）->（），其中包含线程1：EXC_BREAKPOINT （代码= EXC_ARM_BREAKPOINT，子代码= 0xe7ffdefe）

However, as I run the codes, it always returns fatal error: unexpectedly found nil while unwrapping an Optional value. Looking into the error, I can find it is from Swift._fatalErrorMessage (Swift.StaticString, Swift.StaticString, Swift.StaticString, Swift.Uint) -> () with Thread 1: EXC_BREAKPOINT (code=EXC_ARM_BREAKPOINT, subcode=0xe7ffdefe)

我没有使用.continueWithBlock或.continueWithSuccessBlock cuz都无法捕获错误。

I didn't use .continueWithBlock or .continueWithSuccessBlock cuz neither helps to catch the error.

知道为什么吗？谢谢

推荐答案

您需要获取 AWSDynamoDB 的实例，如下所示：

You need to get an instance of AWSDynamoDB as follows:

let dynamoDB = AWSDynamoDB.defaultDynamoDB()

您正在使用默认的-init 方法，不带任何参数，这会导致 AWSDynamoDB 实例没有 AWSServiceConfiguration 。

You are using the default - init method without any parameter, and it causes AWSDynamoDB instance to have no AWSServiceConfiguration.

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