从打字稿节点中的异步等待中获取未定义

Question

用例： 我正在尝试使用 Node 和打字稿在亚马逊 QLDB 中插入一条记录。我能够成功插入 record/document，它 return 是 return.

中的 documentID

有 2 个控制器：EntityController 和 CommonController -EntityController 扩展 CommonController -EntityController 具有获取 req 对象并将其转换为模型对象的代码以及从 CommonController 扩展而来的调用 insert() 函数的代码。

问题我试图将该 documentID 一直传播到我的 API 调用，但不知何故我在 EntityController 中变得不确定。而我能够在 CommonController 中打印 documentID。

我不确定为什么当我清楚地return输入一个值时我会变得不确定。

const CommonController = require("../template/controller");
import { Request, Response } from 'express';
const tableName:string = "entities";
const EntityModel = require("./model")

class EntityController extends CommonController {
    async insertEntitiy(req:Request,res:Response) {
    async insertEntitiy(req:any,res:any) {
        console.log(req);
        console.log("===========");
        console.log(req.body);
        let entity = new EntityModel();
        entity.balance = req.body.balance;
        entity.firstName = req.body.firstName;
        entity.lastName = req.body.lastName;
        entity.email = req.body.email;
        try {
            let documentIds = await this.insert(tableName,entity);
            console.log("--------- inside insertEntity fiunction()---------");
            console.log(documentIds);
            console.log("------------------");
            res.status(200).send(documentIds[0]);
        } catch (error) {
            console.error(`error in creating Entity: ${error}`);
            res.status(500).send({ errMsg: `error in creating Entity: ${error}` });
        }
    } 
}

module.exports = new EntityController();

import { createQldbWriter, QldbSession, QldbWriter, Result, TransactionExecutor } from "amazon-qldb-driver-nodejs";
import { Reader } from "ion-js";
import { error, log } from "../qldb/LogUtil";
import { getFieldValue, writeValueAsIon } from "../qldb/Util";
import { closeQldbSession, createQldbSession } from "../qldb/ConnectToLedger";

module.exports = class Conroller {
  async insert(tablename:string, object:any): Promise<Array<string>> {
    let session: QldbSession;
    let result:Array<string>;
    try {
        session = await createQldbSession();
        await session.executeLambda(async (txn) => {
            result =  await this.insertDocument(txn,tablename,object);
            console.log("---------result inside insert fiunction()---------");
            console.log(result);
            console.log("------------------");
            return (Promise.resolve(result));
          })
    } catch (e) {
        error(`Unable to insert documents: ${e}`);
        return(["Error"]);
    } finally {
        closeQldbSession(session);
    }
  }

  /**
  * Insert the given list of documents into a table in a single transaction.
  * @param txn The {@linkcode TransactionExecutor} for lambda execute.
  * @param tableName Name of the table to insert documents into.
  * @param documents List of documents to insert.
  * @returns Promise which fulfills with a {@linkcode Result} object.
  */
  async  insertDocument(
    txn: TransactionExecutor,
    tableName: string,
    documents: object
  ): Promise<Array<string>> {
    const statement: string = `INSERT INTO ${tableName} ?`;
    const documentsWriter: QldbWriter = createQldbWriter();
    let documentIds: Array<string> = [];
    writeValueAsIon(documents, documentsWriter);
    let result: Result = await txn.executeInline(statement, [documentsWriter]);
    const listOfDocumentIds: Reader[] = result.getResultList();
    listOfDocumentIds.forEach((reader: Reader, i: number) => {
      documentIds.push(getFieldValue(reader, ["documentId"]));   
    });
    console.log("---------documentIds---------");
    console.log(documentIds);
    console.log("------------------");
    return (documentIds);
  }
}

输出： ----------documentIds---------

['4o5UZjMqEdgeENqbP9l7Uhz']

------------插入函数()中的结果---------

['4o5UZjMqEdgeENqbP9l7Uhz']

--------- insertEntity 函数() 内部---------

未定义

Answer 1

正如@daniel-w-strimpel 在评论中指出的那样，您的插入方法 return 仅在 catch 部分。

试试这个：

insert(tablename:string, object:any): Promise<Array<string>> {
  let session: QldbSession;
  let result: Array<string>;
  try {
    session = await createQldbSession();
    return session.executeLambda(async (txn) => {
      result = await this.insertDocument(txn,tablename,object);
      console.log("---------result inside insert fiunction()---------");
      console.log(result);
      console.log("------------------");
      return result;
    })
  } catch (e) {
    error(`Unable to insert documents: ${e}`);
    return(["Error"]);
  } finally {
    closeQldbSession(session);
  }
}
...

在return session.executeLambda你return的承诺。

在return result;你return的实际值。

更多关于这里的承诺：https://pouchdb.com/2015/05/18/we-have-a-problem-with-promises.html

从打字稿节点中的异步等待中获取未定义

getting undefined from async await in typescript node

node.js

typescript

amazon-qldb

['4o5UZjMqEdgeENqbP9l7Uhz']

['4o5UZjMqEdgeENqbP9l7Uhz']

未定义