在 appsync graphql 中过滤一对多的精确数据

Question

我模拟了这个：

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
          }
        }
      }
    }
  }
}

我收到的回复是：

{
  "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？我的模型是错误的模型吗？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：

The response mapping template is written with the Apache Velocity templating language (VTL) and translates the results of the resolver back into 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。

此处有更多详细信息：https://docs.aws.amazon.com/appsync/latest/devguide/resolver-mapping-template-reference-programming-guide.html

在 appsync graphql 中过滤一对多的精确数据

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