TypeScript Ramda propOr return type

Question

I'm composing a Redux selector with Ramda in TypeScript:

const getAvatar = pipe(
  getCurrentUsersProfile,
  propOr('/images/default-avatar.png', 'avatar'),
);

The tooltip for getAvatar says it returns unknown.

With the prop function I can assert a return type like this:

const getCurrentUsersId = pipe(
  getUserProfileSlice,
  prop<'currentUsersId'>('currentUsersId'),
);

How can I get it to know that propOr always returns a string?

Answer 1

The pipe function excepts a list of types. The 1st type is the input of the 1st function, and the other denote the return type of each function in order. The last type is the result of the last function, and the entire pipe.

type Store = {}; // type of your redux store
type UserProfile = {}; // type of the UserProfile slice

const getAvatar = pipe<Store, UserProfile, string>(
  getCurrentUsersProfile,
  propOr('/images/default-avatar.png', 'avatar'),
);

Old answer:

You can explicitly type the propOr call, and add the return value (stackblitz):

import { pipe, propOr } from 'ramda';

const getCurrentUsersProfile = () => {};

const getAvatar = pipe(
  getCurrentUsersProfile,
  propOr('/images/default-avatar.png', 'avatar') as (src: any) => string,
);