在 appsync graphql 中过滤一对多精确数据

Posted 2023-03-08

【中文标题】在 appsync graphql 中过滤一对多精确数据

【英文标题】：Filter one to many exact data in appsync graphql

【发布时间】：2020-12-11 09:37:34

【问题描述】：

我已经模拟了这个：

type FreightDriver
  @model
  @key(
    name: "byCityByState"
    fields: ["state", "city"]
    queryField: "freightDriversByStateByCity"
  ) 
  id: ID!
  name: String!
  state: String!
  city: String!
  trucks: [Truck] @connection(keyName: "byFreightDriver", fields: ["id"])


type Truck
  @model
  @key(name: "byFreightDriver", fields: ["freightDriverId", "tons"]) 
  id: ID!
  freightDriverId: ID!
  boxId: ID!
  brand: String!
  model: String!
  tons: Float!
  box: Box @connection(fields: ["boxId"])


type Box @model 
  id: ID!
  type: String!
  width: Float!
  height: Float!
  depth: Float!

我正在像这样查询数据：

query 
  freightDriversByStateByCity(state: "Jalisco", city:  eq: "Guadalajara" ) 
    items 
      id
      name
      city
      state
      trucks(tons:  eq: 12 ) 
        items 
          brand
          model
          box 
            type
          
        
      
    
  

我得到了这样的回应：

  "data": 
    "freightDriversByStateByCity": 
      "items": [
        
          "id": "aebb6696-573d-41ed-894e-22b69264cace",
          "name": "Diey",
          "city": "Guadalajara",
          "state": "Jalisco",
          "trucks": 
            "items": [
              
                "brand": "chevrolet",
                "model": "12",
                "box": 
                  "type": "Refrigerada"
                
              
            ]
          
        ,
        
          "id": "6e8e6772-61e7-47d6-b134-d615a3c65f62",
          "name": "Roberto Mendez",
          "city": "Guadalajara",
          "state": "Jalisco",
          "trucks": 
            "items": []
          
        ,
        
          "id": "d314808c-64e7-421d-b83b-008177ab6b25",
          "name": "Roberto Mendez",
          "city": "Guadalajara",
          "state": "Jalisco",
          "trucks": 
            "items": []
          
        ,
        
          "id": "19847d0c-185c-48f6-9e5c-435e3907133a",
          "name": "Andrés",
          "city": "Guadalajara",
          "state": "Jalisco",
          "trucks": 
            "items": [
              
                "brand": "chevrolet",
                "model": "1234",
                "box": 
                  "type": "Refrigerada"
                
              ,
              
                "brand": "chevrolet",
                "model": "1234",
                "box": 
                  "type": "Grúa"
                
              ,
              
                "brand": "chevrolet",
                "model": "12",
                "box": 
                  "type": "Refrigerada"
                
              
            ]
          
        ,
        
          "id": "2c4c9e3a-bfe5-4d4e-bee7-3eddb1b8ef1b",
          "name": "Roberto Mendez ",
          "city": "Guadalajara",
          "state": "Jalisco",
          "trucks": 
            "items": []
          
        ,
        
          "id": "cb4eb22c-aa54-416e-aecc-305a18bc9c83",
          "name": "Roberto Mendez",
          "city": "Guadalajara",
          "state": "Jalisco",
          "trucks": 
            "items": []
          
        
      ]
    
  

如果你检查，有一些是这样的：

"trucks": 
  "items": []

我怎样才能避免它们？我的模型是不是模型错误？谢谢！

【参考方案1】：

您可以使用映射模板在响应数据返回给客户端之前对其进行修改：

响应映射模板使用 Apache Velocity 模板语言 (VTL) 编写，并将解析器的结果转换回 GraphQL。

在这种情况下，您可以检查 trucks.items 是否为空，如果是，请在返回之前从 trucks 中删除 items 数组。

更多详情：https://docs.aws.amazon.com/appsync/latest/devguide/resolver-mapping-template-reference-programming-guide.html

【讨论】：

谢谢！上帝保佑你:)