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Rust Result in Typescript
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| /** made by Dan Imhoff, the code below is copy-pasted from https://www.huy.rocks/everyday/02-14-2022-typescript-implement-rust-style-result */ | |
| export type Result<T, E = undefined> = { ok: true; value: T } | { ok: false; error: E | undefined } | |
| export const Ok = <T>(data: T): Result<T, never> => ({ ok: true, value: data }) | |
| export const Err = <E>(error?: E): Result<never, E> => ({ ok: false, error }) |
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| import { type Result, Ok, Err } from "./result" | |
| const numberIsLessThan10 = (num: number): Result<number, string> => { | |
| if (num < 10) return Ok(num) | |
| return Err("number is not less than 10") | |
| } | |
| const number = numberIsLessThan10(5) | |
| if (number.ok) useNumber(number.value) // ok | |
| else if (number.error) console.trace(number.error) // known error | |
| else console.trace("unknown error") // unknown error |
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| const fetchGeoJson = async (): Promise<Result<GeoJson, string>> => { | |
| const res = await fetch(`/api`) | |
| const json = await res.json() | |
| if (!json) return Err("could not get json from api") | |
| if (!validate(json.geo)) return Err("did not get valid geo json from api") | |
| return Ok(json.geo) | |
| } | |
| const geoJson = await fetchGeoJson() | |
| if (geoJson.ok) useGeoJson(geoJson.value) // ok | |
| else if (geoJson.error) console.trace(geoJson.error) // known error | |
| else console.trace("unknown error") // unknown error |
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