如何让Amplify DataStore查询返回关联子项？

一、用DataStore显式加载关联并过滤子项 #

DataStore默认不会自动加载关联模型，必须通过include参数指定，同时可以给子模型加过滤条件排除软删除的项：

import { DataStore } from '@aws-amplify/datastore';
import { TestResults, TestResultData } from './models';

// 基础查询，加载带过滤的TestResultData关联
const loadTestResults = async () => {
  const testResults = await DataStore.query(TestResults, undefined, {
    include: [
      {
        model: TestResultData,
        // 过滤掉已软删除的子项
        predicate: TestResultData.NOT(TestResultData._IS_DELETED(true))
      }
    ]
  });
  return testResults;
};

二、结合分页的写法 #

要保持分页正常，只需在查询参数里加上limit和nextToken即可，和include兼容：

const loadTestResultsWithPagination = async () => {
  let allResults = [];
  let nextToken;

  do {
    const { items, nextToken: newToken } = await DataStore.query(TestResults, undefined, {
      include: [
        {
          model: TestResultData,
          predicate: TestResultData.NOT(TestResultData._IS_DELETED(true))
        }
      ],
      limit: 10, // 每页10条
      nextToken
    });
    
    allResults = [...allResults, ...items];
    nextToken = newToken;
  } while (nextToken);

  return allResults;
};

三、排查关联不生效的常见原因 #

1. 模型字段大小写匹配：Amplify生成的模型会把Schema中的大写字段转为驼峰式，比如Schema里的TestResultData在模型中可能是testResultData，确保include里引用的是生成模型的正确名称（检查./models/index.js确认）。
2. 重新生成模型：如果修改过Schema，务必运行amplify codegen models更新模型代码，避免关联映射错误。
3. 确认软删除机制：Amplify默认使用软删除，所有删除的项会标记_isDeleted: true，必须显式过滤，否则会被返回。

四、如果用GraphQL API直接查询的解决方案 #

若你更倾向于直接调用GraphQL API，可以自定义查询，在服务端过滤已删除项并保留分页：

自定义GraphQL查询 #

query ListTestResults($limit: Int, $nextToken: String) {
  listTestResults(limit: $limit, nextToken: $nextToken) {
    items {
      id
      CustomerID
      lab
      fasting
      dateReported
      # 其他TestResults字段
      # 过滤子项中的已删除记录
      testResultData(filter: {_isDeleted: {eq: false}}) {
        items {
          id
          name
          value
          unit
          # 其他TestResultData字段
        }
      }
    }
    nextToken
  }
}

客户端调用 #

import { API, graphqlOperation } from '@aws-amplify/api';

const fetchTestResultsViaAPI = async () => {
  let allResults = [];
  let nextToken;

  do {
    const response = await API.graphql(graphqlOperation(`
      query ListTestResults($limit: Int, $nextToken: String) {
        listTestResults(limit: $limit, nextToken: $nextToken) {
          items {
            id
            CustomerID
            lab
            testResultData(filter: {_isDeleted: {eq: false}}) {
              items {
                id
                name
                value
              }
            }
          }
          nextToken
        }
      }
    `, { limit: 10, nextToken }));

    const { items, nextToken: newToken } = response.data.listTestResults;
    allResults = [...allResults, ...items];
    nextToken = newToken;
  } while (nextToken);

  return allResults;
};

内容的提问来源于stack exchange，提问作者Max