[英]getting undefined from async await in typescript node
用例:我正在尝试使用 Node 和 typescript 在 amazon QLDB 中插入一条记录。 我能够成功插入记录/文档,并返回给我 documentID 作为回报。
有 2 个控制器: EntityController和CommonController -EntityController extends CommonController -EntityController 具有获取 req 对象的代码,将其转换为模型对象,并调用从 CommonController 扩展的 insert() 函数。
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 中未定义。 而我可以在 CommonController 中打印 documentID。
当我明确返回一个值时,我不确定为什么我变得未定义。
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---------
---------插入函数()内的结果---------
--------- 在 insertEntity 函数()中---------
正如@daniel-w-strimpel 在评论中指出的那样,您的 insert 方法仅在 catch 部分返回。
尝试这个:
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
您返回 Promise。
return result;
您返回实际值。
更多关于这里的承诺: https : //pouchdb.com/2015/05/18/we-have-a-problem-with-promises.html
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