Typescript (Type 'undefined' is not assignable to type) Why is my Array having a | undefined?
Solution 1
The problem was that in my filterByExchangeBase
util function, I used .map
instead of .filter
which would result in some undefined
objects in that array. Switching to filter made sure that only existing items would make it into the array.
...
Update: By changing .map to .filter, the price_quote updates didn't take
Refactored the logic to make sure that btcMarkets and ethMarkets aren't used if they will be empty.
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;
});
}
Solution 2
Why is combinedMarkets an array either and object of type IMarketAsset or undefined
Because any of the marketXXX
arrays, is an array of IMarketAsset | undefined
(instead of just IMarketAsset
.
Leon Gaban
Investor, Powerlifter, Crypto investor and global citizen You can also find me here: @leongaban | github | panga.ventures
Updated on July 11, 2022Comments
-
Leon Gaban almost 2 years
I have an array called
combinedMarkets
which is either a combination of 5 or 3 different market arrays. All these arrays have the following interfaceIMarketAsset[]
:export interface IMarketAsset { exchange: string; base: string; quote: string; price_quote: string; timestamp: string; }
Here is where the typescript error occurs:
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) : [];
Argument of type '({ price_quote: string; exchange: string; base: string; quote: string; timestamp: string; } | undefined)[]' is not assignable to parameter of type 'IMarketAsset[]'. Type '{ price_quote: string; exchange: string; base: string; quote: string; timestamp: string; } | undefined' is not assignable to type 'IMarketAsset'. Type 'undefined' is not assignable to type 'IMarketAsset'.ts(2345)
const combinedMarkets: ({ price_quote: string; exchange: string; base: string; quote: string; timestamp: string; } | undefined)[]
Why is combinedMarkets an array of either an object of type
IMarketAsset
or undefined?Full combineExchangeData Function
// 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) } } }); };
Util functions
Here are the 2 other util functions I use in the main function. Also I have narrowed down the problem to the
btcMarkets
andethMarkets
arrays. So looking atfilterByExchangeBase
.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; } }) : []; }
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Leon Gaban about 5 yearsYeah I'm trying to figure out why that is, I think I've narrowed it down to
combinedMarkets
sometimes containing empty arrays during theconcat
part of the logic, so will try filtering out empty arrays. -
Leon Gaban about 5 years? but each array is of the same type
IMarketAsset
so when I concated all of them, they are still of typeIMarketAsset
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Leon Gaban about 5 yearsCould you post an example of this
type
You are correct in that I need a type that supports bothIMarketAsset
and undefined in an array. -
Leon Gaban about 5 yearsOk my fix doesn't really fix the problem. I have to use
export const filterCryptoBase = (exchanges: IMarketAsset[] | any
to avoid a typescript error. Will offer this for bounty tomorrow.