Typescript override deep key

Question

Let's say I have an interface like this one

interface Theme {
  a: {
    b?: {
      c: CustomType;
    }
  }
  ...
}

how do I override this theme interface into a new one changing b to always defined?? (Removing ?) obviously I'd like to keep everything else the same.

EDIT: I don't have access to CustomType

score 1 · Accepted Answer · answered Feb 03 '20 at 11:51

1

Try this:

type NewTheme = Theme & {
  a: {
    b: NonNullable<Theme['a']['b']>
  }
}

Playground

answered Feb 03 '20 at 11:51

Shalom Peles

2,285
8
21

score 0 · Answer 2 · answered Feb 03 '20 at 11:35

0

Because parameter?: type is a shorthand for parameter: type | undefined you can override interface:

interface Theme1 extends Theme {
  a: {
    b: {
      c: CustomType;
    }
  }
}

answered Feb 03 '20 at 11:35

Masih Jahangiri

9,489
3
45
51

1

Wouldn't this remove all the other theme properties? – Leonardo Drici Feb 03 '20 at 11:38
Plus I don't have access to CustomType – Leonardo Drici Feb 03 '20 at 11:40
This method keeps all the other `theme` properties but not for you if haven't access to `CustomType`. – Masih Jahangiri Feb 03 '20 at 12:28

Typescript override deep key

2 Answers2