Retuple Symbols

Implement a custom result-like by implementing ResultLike on a class or object. An object with this implementation can be converted to a Result by the retuple library and can be used in most places where a Result is required.

Creating a custom Result

import { ResultLikeSymbol, type ResultLike } from "retuple-symbols";

class CustomResult<T> implements ResultLike<T, CustomError> {
  value: T;

  constructor(value: T) {
    this.value = value;
  }

  [ResultLikeSymbol]() {
    return this.value === "test"
      ? { ok: true as const, value: this.value }
      : { ok: false as const, value: "Value was not test" };
  }
}

Using a custom Result

import { Result, Ok } from "retuple";

const custom = new CustomResult("test");
const result: Result<string, Error> = Result(custom);

const chain = Ok("test")
 .$andThen((val) => new CustomResult(val))
 .$tap((val) => console.log(`Value should be test:`, val))
 .$map((val) => "not test")
 .$andThen((val) => new CustomResult(val))
 .$tapErr((err) => console.log(`Should be error message:`, err))
 ...