True Myth / task / safeNullable
Function: safeNullable()
Call Signature
safeNullable<
F,P,R>(fn): (...params) =>Task<Maybe<NonNullable<R>>,unknown>
Given a function which returns a Promise of a nullable type, return a new function with the same parameters but which returns a Task of a Maybe instead.
If you wish to transform the error directly, rather than with a combinator, see the other overload, which accepts an error handler.
This is basically just a convenience for something you could do yourself by chaining safe with Maybe.of:
import Maybe from 'true-myth/maybe';
import { safe, safeNullable } from 'true-myth/task';
async function numberOrNull(value: number): Promise<number | null> {
return Math.random() > 0.5 ? value : null;
}
// Using this helper
const safeNumberOrNull = safeNullable(numberOrNull);
// Using `safe` and `Maybe.of` manually
const moreWorkThisWay= safe(numberOrNull);
let theTask = moreWorkThisWay(123).map((n) => Maybe.of(n));The convenience is high, though, since you can now use this to create fully safe abstractions to use throughout your codebase, rather than having to remember to do the additional call to map the Task’s resolution value into a Maybe at each call site.
Type Parameters
F
F extends (...params) => PromiseLike<unknown>
P
P extends never[]
R
R extends any
Parameters
fn
F
A function to wrap so it never throws an error or produces a Promise rejection.
Returns
Parameters
params
...P
Returns
Task<Maybe<NonNullable<R>>, unknown>
Call Signature
safeNullable<
F,P,R,E>(fn,onError): (...params) =>Task<Maybe<NonNullable<R>>,E>
Given a function which returns a Promise and a function to transform thrown errors or Promise rejections resulting from calling that function, return a new function with the same parameters but which returns a Task.
To catch all errors but leave them unhandled and unknown, see the other overload.
This is basically just a convenience for something you could do yourself by chaining safe with Maybe.of:
import Maybe from 'true-myth/maybe';
import { safe, safeNullable } from 'true-myth/task';
async function numberOrNull(value: number): Promise<number | null> {
return Math.random() > 0.5 ? value : null;
}
// Using this helper
const safeNumberOrNull = safeNullable(numberOrNull);
// Using `safe` and `Maybe.of` manually
const moreWorkThisWay= safe(numberOrNull);
let theTask = moreWorkThisWay(123).map((n) => Maybe.of(n));The convenience is high, though, since you can now use this to create fully safe abstractions to use throughout your codebase, rather than having to remember to do the additional call to map the Task’s resolution value into a Maybe at each call site.
Type Parameters
F
F extends (...params) => PromiseLike<unknown>
P
P extends never[]
R
R extends any
E
E
Parameters
fn
F
A function to wrap so it never throws an error or produces a Promise rejection.
onError
(reason) => E
A function to use to transform the
Returns
Parameters
params
...P