Aws Appsync 解析器：如何创建解析器以更新列表映射 (DynaMoDB) 中的项目

Posted 2023-03-08

【中文标题】Aws Appsync 解析器：如何创建解析器以更新列表映射 (DynaMoDB) 中的项目

【英文标题】：Aws Appsync Resolver : How to create a resolver to update item in list map (DynaMoDB)

【发布时间】：2019-10-14 13:59:06

【问题描述】：

我在一个表中创建多个对象，我在这里有一个名为“用户”的示例 DynamoDB 表，其中包含字段（名字、姓氏、电子邮件、公司），有人可以知道如何创建解析器以在历史记录中添加新项目?谢谢。

  "id": "d7913a57-f458-4b81-8d6e-10f81e2b1dc2",
  "firstName": "John",
  "lastName": "Doe",
  "email": "[e-mail]",
  "companies" : [
      
        "companyId": "6059be51-1e66-4f3a-9c8f-ced3bc89d562",
        "createdAt": 321321,
        "histories": [
          
           "companyHistoryId": "dc9d1a57-fb82-4c25-a6cf-d27dfe114f8f",
           "content": "Company A was created.",
           "createdAt": 321321,
           "createdBy": "d7913a57-f458-4b81-8d6e-10f81e2b1dc2"
          
        ],
     ,
  ]

这是我用来添加新公司的解析器

    "version" : "2017-02-28",
    "operation" : "UpdateItem",
    "key" : 
        "id":  "S": "$context.arguments.id" ,
    ,
    "update" : 
        "expression" : "SET companies = list_append(if_not_exists(companies, :emptyList), :newCompany)",
        "expressionValues" : 
            ":emptyList":  "L" : [] ,
            ":newCompany" :  "L" : [
                 "M": 
                    "name":  "S" : "$context.arguments.name" ,
                    "createdAt":  "N" : "$context.arguments.createdAt" ,
                    "companyId":  "S": "$util.autoId()" ,
                    "isActive":  "BOOL" : true ,
                    "histories":  "L": [
                         "M": 
                            "companyHistoryId":  "S": "$util.autoId()" ,
                            "content" :  "S" : "$context.arguments.name was created." ,
                            "createdAt":  "N" : "$context.arguments.createdAt" ,
                            "createdBy":  "S": "$context.arguments.id" 
                        
                    ] 
                
            ] ,
        
    

【参考方案1】：

试试这个：

  "version" : "2017-02-28",
  "operation" : "UpdateItem",
  "key" : 
      "id":  "S": "$context.arguments.id" ,
  ,
  "update" : 
      "expression" : "SET companies[$ctx.args.index].histories = list_append(if_not_exists(companies[$ctx.args.index].histories, :emptyList), :history)",
      "expressionValues" : 
          ":emptyList":  "L" : [] ,
          ":history" :  "L": [
               "M": 
                  "companyHistoryId":  "S": "$util.autoId()" ,
                  "content" :  "S" : "$context.arguments.name was created." ,
                  "createdAt":  "N" : "$context.arguments.createdAt" ,
                  "createdBy":  "S": "$context.arguments.id" 
              
          ] 
      
  

记得传递$ctx.args.index，这是companies项目的索引，histories将被更新。