Question

我正在尝试使用reduce将我的SQL响应总结为两个类别，即收入和结果，但是我得到的是“ currentValue”（交易）类型作为返回而不是累加器（BalanceDTO），我仅返回累加器，如何将事务类型作为返回类型？

我真的不知道自己在做什么错，最近两个小时我完全被困住了。

import { getRepository } from 'typeorm';

import Transaction from '../models/Transaction';

interface BalanceDTO {
  income: number;
  outcome: number;
}

class GetBalanceService {
  public async execute(): Promise<BalanceDTO> {
    const transactionRepository = getRepository(Transaction);

    const transactions = await transactionRepository.find();

    const balance = transactions.reduce(
      (accumulator: BalanceDTO, transaction): BalanceDTO => {
        accumulator[transaction.type] += transaction.value;
        return accumulator; //// HERE -- How it is returning the transactions type? ////
      },
    );

    return balance;
  }
}

export default GetBalanceService;

Answer 1

您缺少定义初始值和初始值的类型。初始值的类型将定义df.groupBy('State1').count().show() Py4JJavaError Traceback (most recent call last) org.apache.spark.SparkException: Job aborted due to stage failure: Task 1 in stage 725.0 failed 1 times, most recent failure: Lost task 1.0 in stage 725.0 (TID 13480, localhost, executor driver): java.util.regex.PatternSyntaxException: Dangling meta character '*' near index 0函数的返回类型。

我建议将初始值定义为BalanceDTO，起始值为零

reduce

现在，const balance = transactions.reduce((accumulator, transaction) => { accumulator[transaction.type] += transaction.value; return accumulator; }, { income: 0, outcome: 0, } as BalanceDTO); // initialValue as a BalanceDTO是BalanceDTO

Answer 2

您需要传递exams2pdf()的初始值作为exams2pdf()函数的第二个参数：

accumulator

Answer 3

尝试这个。

    const balance = transactions.reduce(
      (accumulator: BalanceDTO, transaction): BalanceDTO => {
        accumulator[transaction.type] += transaction.value;
        return accumulator;
      },{income: 0, outcome: 0} //you'd better set the initial value
    );

https://developer.mozilla.org/ko/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

打字稿减少返回错误的打字稿

3 个答案: