如何从 TS 文字联合类型推断 object 的键和值？

Question

i have two literal union types of strings and want them to be the possible keys and values of an object.

export type AlarmKeyword = 'R1' | 'R2';

export type ResourceTypes = 'nktw' | 'rtw' | 'nef' | 'rth' | 'hlf' | 'dlk';

The new type looks like this:

export type AlarmKeywordObject = {
  [P in AlarmKeyword]: { [T in ResourceTypes]: number };
};

But TS now complains about this code:

      {
        R1: {
          rtw: 1,
        },
      }

Type '{ rtw: number; }' is missing the following properties from type '{ nktw: number; rtw: number; nef: number; rth: number; hlf: number; dlk: number; }': nktw, nef, rth, hlf, dlk

How can i ensure, that the keys are optional and not all of them are required?

Thank you!

Answer 1

You can use question mark ? to mark that keys are optional:

type AlarmKeywordObject = {
    [P in AlarmKeyword]?: { [T in ResourceTypes]?: number }
};

Playground