在 appsync graphql 中过滤一对多的精确数据

Question

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!
}

我正在查询这样的数据：

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

我得到的回应是：

{
  "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": []
          }
        }
      ]
    }
  }
}

如果你检查一下，有一些是这样的：

"trucks": {
  "items": []
}

我怎样才能避免它们？ 我的model是错的model吗？ 谢谢！

Answer 1

您可以使用映射模板在返回给客户端之前修改响应数据：

响应映射模板使用 Apache 速度模板语言 (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，则在返回之前从trucks中删除items数组。

更多细节在这里： https://docs.aws.amazon.com/appsync/latest/devguide/resolver-mapping-template-reference-programming-guide.html