How to work with Records in fp-ts

[adinvadim]

How can I work with Records in fp-ts. Want to assign other records, remove keys etc, buy always has an error, that I cant have optional properties in Record

Property 'a' is optional in type 'R' but required in type 'Record<keyof R, string | number | undefined>

Example

interface A {
  a?: string;
  b: string;
  c: number;
}

const fn = (r: A) => pipe(
  r,
  R.deleteAt('c'),
)

This code throw type error

Property 'a' is optional in type 'R' but required in type 'Record<keyof R, string | number | undefined>

[mlegenhausen]

Types with a fixed index signature like an interface are not records. A record has for each possible key always the same value type. Your interface A is called a struct in fp-ts terms. It is recommended not to use any record functions on these types. If you want to remove a key from a struct you should define a function that transforms between the two types.

interface A {
  a?: string;
  b: string;
  c: number;
}

interface B extends Omit<A, 'a'> {}

function fn({ a, ...rest }: A): B {
    return rest
}