Use string fields as keys in type definitions

Question

I have a Props type that looks as follows

type Props<FormData> = {
    formData: FormData,
    sectionNme: keyof FormData,
    name: string
}

but what I'd like is something akin to

type Props<FormData> = {
    formData: FormData,
    sectionNme: keyof FormData,
    name: keyof FormData[sectionName]
}

but I can't seem to access the sectionName field in this type definition. Is there a better way to type this, other than just string?

Could you give an example object how it should look like?

Murat Karagöz
– Murat Karagöz

2020-07-13 12:51:53 +00:00
Commented Jul 13, 2020 at 12:51 — Murat Karagöz
– Murat Karagöz, Commented Jul 13, 2020 at 12:51

Karol Majewski · Accepted Answer · 2020-07-13 12:55:52Z

1

Introduce a second type parameter:

type Props<FormData extends object, K extends keyof FormData = keyof FormData> = {
    formData: FormData,
    sectionNme: K,
    name: keyof FormData[K]
}

Usage:

interface MyForm {
    foo: {
        bar: string;
    }
}

const props: Props<MyForm> = {
    formData: {
        foo: {
            bar: 'hello'
        }
    },
    sectionNme: 'foo',
    name: 'bar',
}

answered Jul 13, 2020 at 12:55

Karol Majewski

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