Typescript（类型'undefined'不能分配给类型）为什么我的数组有一个|号？未定义？

Question

我有一个名为combinedMarkets的数组，它是5个或3个不同市场数组的组合。所有这些数组都具有以下接口IMarketAsset[]：

export interface IMarketAsset {
  exchange: string;
  base: string;
  quote: string;
  price_quote: string;
  timestamp: string;
}

出现打字稿错误的地方：

const combinedMarkets = asset !== 'BTC' && asset !== 'ETH' ?
  btcMarkets.concat(ethMarkets).concat(marketUSD).concat(marketUSDC).concat(marketUSDT) :
  marketUSD.concat(marketUSDC).concat(marketUSDT);

const filteredMarkets = combinedMarkets.length > 0 ? filterByUSDbase(asset, combinedMarkets) : [];

  

'（{price_quote：string; exchange：string; base：string; quote：string; timestamp：string;} | undefined）[]'类型的参数不能分配给'IMarketAsset []'类型的参数。     输入'{price_quote：string;交换：字符串; base：字符串; quote：字符串;时间戳：字符串； } |未定义”不能分配给“ IMarketAsset”类型。       类型“未定义”不能分配给类型“ IMarketAsset”。ts（2345）

const combinedMarkets: ({
  price_quote: string;
  exchange: string;
  base: string;
  quote: string;
  timestamp: string;
} | undefined)[]

为什么CombinedMarkets是IMarketAsset类型或未定义对象的数组？

完整的CombineExchangeData函数

// Filter by BTC, ETH, USD, USDT or USDC prices
// If asset has BTC/ETH pairing, obtain exchange BTC/ETH price to calculate assets USD/USDT value
export const combineExchangeData =
  (asset: string, { marketBTC, marketETH, marketUSD, marketUSDT, marketUSDC }: IGetMarketsRes) => {
    const btcBasedExchanges = marketBTC.filter((market: IMarketAsset) => market.base === asset);
    const ethBasedExchanges = marketETH.filter((market: IMarketAsset) => market.base === asset);
    const btcUSDTprices = marketUSDT.filter((market: IMarketAsset) => market.base === 'BTC');
    const btcUSDprices = marketUSD.filter((market: IMarketAsset) => market.base === 'BTC');
    const ethUSDTprices = marketUSDT.filter((market: IMarketAsset) => market.base === 'ETH');
    const ethUSDprices = marketUSD.filter((market: IMarketAsset) => market.base === 'ETH');

    const btcPricedMarkets = filterByExchangeBase(btcBasedExchanges, btcUSDTprices, btcUSDprices);
    const ethPricedMarkets = filterByExchangeBase(ethBasedExchanges, ethUSDTprices, ethUSDprices);

    const btcMarkets = btcPricedMarkets.filter((market) => R.not(R.isNil(market)));
    const ethMarkets = ethPricedMarkets.filter((market) => R.not(R.isNil(market)));

    const combinedMarkets = asset !== 'BTC' && asset !== 'ETH' ?
      btcMarkets.concat(ethMarkets).concat(marketUSD).concat(marketUSDC).concat(marketUSDT) :
      marketUSD.concat(marketUSDC).concat(marketUSDT);

    console.log('combinedMarkets', combinedMarkets);
    const filteredMarkets = combinedMarkets.length > 0 ? filterByUSDbase(asset, combinedMarkets) : [];
    console.log('filteredMarkets', filteredMarkets);

    if (R.isEmpty(filteredMarkets)) return [];

    return filteredMarkets.map((market: IMarketAsset) => {
      if (market) {
        return {
          ...market,
          price_quote: formatPrice(market.price_quote)
        }
      }
    });
  };

实用功能

这是我在主函数中使用的另外两个util函数。另外，我已将问题缩小到btcMarkets和ethMarkets数组。因此，请看filterByExchangeBase。

import * as R from 'ramda'

import { USD_CURRENCIES } from '../shared/constants/api'
import { IMarketAsset } from '../shared/types'

const calculateBasePrice = (assetBtcPrice: string | number, btcPrice: string | number) => 
  (Number(assetBtcPrice) * Number(btcPrice)).toString();

export const filterByExchangeBase =
  (exchanges: IMarketAsset[], usdtExchanges: IMarketAsset[], usdExchanges: IMarketAsset[]) =>
    exchanges.map((exchange) => {
      let basePriced = usdtExchanges.filter((btcExchange) => btcExchange.exchange === exchange.exchange)[0];

      if (!basePriced) {
        basePriced = usdExchanges.filter((btcExchange) => btcExchange.exchange === exchange.exchange)[0];
      }

      if (basePriced) {
        const { price_quote: assetBtcPrice } = exchange;
        const { price_quote: btcPrice } = basePriced;

        return {
          ...exchange,
          price_quote: calculateBasePrice(assetBtcPrice, btcPrice)
        }
      }
    });

export const filterByUSDbase = (asset: string, combinedMarkets: IMarketAsset[] | undefined) => {
  if (!combinedMarkets) return [];
  return R.not(R.any(R.equals(asset))(USD_CURRENCIES))
    ? combinedMarkets.filter((marketAsset: IMarketAsset) => {
      if (marketAsset && marketAsset.base) {
        return marketAsset.base === asset;
      }
    }) : [];
}

Answer 1

  

为什么CombinedMarkets是一个数组，且对象类型为IMarketAsset或未定义

因为任何marketXXX数组，所以是IMarketAsset | undefined的数组（而不只是IMarketAsset。

Answer 2

尝试将类型定义为每个选项的数组，而不是将它们组合在一起：

__new__

Answer 3

问题在于，在我的filterByExchangeBase实用函数中，我使用.map而不是.filter，这将导致该数组中的某些undefined对象。切换到过滤器可确保只有现有项目才能将其放入数组。

...

更新：通过将.map更改为.filter，price_quote更新没有进行

重构逻辑以确保如果btcMarkets和ethMarkets为空，则不使用它们。

export const combineExchangeData =
  (asset: string, { marketBTC, marketETH, marketUSD, marketUSDT, marketUSDC }: IGetMarketsRes) => {
    const btcBasedExchanges = marketBTC.filter((market: IMarketAsset) => market.base === asset);
    const ethBasedExchanges = marketETH.filter((market: IMarketAsset) => market.base === asset);
    const btcUSDTprices = marketUSDT.filter((market: IMarketAsset) => market.base === 'BTC');
    const btcUSDprices = marketUSD.filter((market: IMarketAsset) => market.base === 'BTC');
    const ethUSDTprices = marketUSDT.filter((market: IMarketAsset) => market.base === 'ETH');
    const ethUSDprices = marketUSD.filter((market: IMarketAsset) => market.base === 'ETH');

    const btcPricedMarkets = notBTCorETH(asset) ? filterCryptoBase(btcBasedExchanges, btcUSDTprices, btcUSDprices) : [];
    const ethPricedMarkets = notBTCorETH(asset) ? filterCryptoBase(ethBasedExchanges, ethUSDTprices, ethUSDprices) : [];

    const btcMarkets = R.not(R.isEmpty(btcPricedMarkets)) ? btcPricedMarkets.filter((market: IMarketAsset) => R.not(R.isNil(market))) : [];
    const ethMarkets = R.not(R.isEmpty(ethPricedMarkets)) ? ethPricedMarkets.filter((market: IMarketAsset) => R.not(R.isNil(market))) : [];

    const combinedMarkets = notBTCorETH(asset) ?
      btcMarkets.concat(ethMarkets).concat(marketUSD).concat(marketUSDC).concat(marketUSDT) :
      marketUSD.concat(marketUSDC).concat(marketUSDT);

    const filteredMarkets = filterByUSDbase(asset, combinedMarkets);

    if (R.isEmpty(filteredMarkets)) return [];

    return filteredMarkets.map((market: IMarketAsset) => ({
      ...market,
      price_quote: formatPrice(market.price_quote)
    }));
  };

---

export const filterCryptoBase =
  (exchanges: IMarketAsset[] | any, usdtExchanges: IMarketAsset[], usdExchanges: IMarketAsset[]) => {
    return exchanges.map((exchange: IMarketAsset) => {
      let basePriced = usdtExchanges.filter((btcExchange) => btcExchange.exchange === exchange.exchange)[0];
      if (!basePriced) {
        basePriced = usdExchanges.filter((btcExchange) => btcExchange.exchange === exchange.exchange)[0];
      }

      if (exchange && basePriced && exchange.price_quote && basePriced.price_quote) {
        const { price_quote: assetBtcPrice } = exchange; // Asset price in BTC/ETH
        const { price_quote: usdPrice } = basePriced; // BTC/ETH price in USDT/USD
        const price_quote = calculateBasePrice(assetBtcPrice, usdPrice).toString();

        return {
          ...exchange,
          price_quote
        }
      }

      return null;
    });
  }