增加AWS DynamoDB中的Number属性目标C. [英] Incrementing Number Property in AWS DynamoDB Objective C

问题描述

我正在努力增加我在DynamoDB表格中保存的项目的数字属性值，我的代码目前是：

I am struggling with incrementing a number property value of an item already saved in my table on DynamoDB my code currently is:

        AWSDynamoDBUpdateItemInput *updateItemInput = [AWSDynamoDBUpdateItemInput new];
        updateItemInput.tableName = @"Table";

        updateItemInput.key= @{
                               @"KeyPropertyName":@"KeyValue"
                                };
        updateItemInput.updateExpression = @"SET(counter = counter + :val)";
        updateItemInput.expressionAttributeValues =@{
                                                     @":val":@1
                                                     };
        AWSDynamoDB *dynamoDB = [AWSDynamoDB defaultDynamoDB];

        [[dynamoDB updateItem:updateItemInput]
         continueWithBlock:^id(AWSTask *task) {
             if (task.error) {
                 NSLog(@"The request failed. Error: [%@]", task.error);
             }
             if (task.exception) {
                 NSLog(@"The request failed. Exception: [%@]", task.exception);
             }
             if (task.result) {
                 //Do something with result.
             }
             return nil;
         }];

当我没有注释掉updateExpression和expressionAttributeValues时，我的应用程序总是崩溃。当我创建一个我的项类型的空实例时，我可以到达块，当我创建一个AWSDynamoDBAttributeValue实例传入密钥时，会得到奇怪的结果。有什么建议么？我是否也不正确地编写了我的updateExpression？

My app always crashes when I do not comment out the updateExpression and expressionAttributeValues. I can reach the block when I create an empty instance of my item type and get strange results when I create an instance of AWSDynamoDBAttributeValue to pass in the key. Any suggestions? Am I also improperly writing my updateExpression?

我还将在另一个对象上添加更新和删除数组/列表和字典/地图属性中的项目。这会有什么不同？

I am also going to be adding updating and deleting items in array/list and dictionary/map properties on another object. How would this differ?

推荐答案

有几件事情。 key 的定义如下：

There are a couple of things. key is defined as follows:

@property (nonatomic, strong) NSDictionary<NSString *, AWSDynamoDBAttributeValue *> * _Nullable key;

您需要更换 @KeyValue实例 AWSDynamoDBAttributeValue 。

expressionAttributeValues 已定义如下：

@property (nonatomic, strong) NSDictionary<NSString *, AWSDynamoDBAttributeValue *> * _Nullable expressionAttributeValues;

您需要将 @ 1 替换为 AWSDynamoDBAttributeValue 的实例。

You need to replace @1 with an instance of AWSDynamoDBAttributeValue.

确保使用最新版本的AWS SDK for iOS，以便您可以看到头文件中的泛型注释。它可以帮助您构建正确的请求对象。

Make sure to use the latest version of the AWS SDK for iOS so that you can see the generics annotations in the header file. It helps you construct the proper request object.

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