typescript use keys as restriction for strings

Question

I have the following interface:

interface Address {
   street: string
   town: string
   country: string
}

I want a function to accept a key parameter that has to be one of three strings:

function useKey(key: "street" | "town" | "country") {
}

Can I somehow generate the type for the key parameter from the interface?

Titian Cernicova-Dragomir · Accepted Answer · 2018-09-19 13:45:23Z

4

Typescript has the keyof type operator for this exact specific case:

function useKey(key: keyof Address ) {
}

This will give you all the public keys of a type in a union.

You can use type queries to even get to the type of the filed:

function getValue<K extends keyof Address>(key: K): Address[K]{
     //...
}

answered Sep 19, 2018 at 13:45

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Comments

Aleksey L. · Accepted Answer · 2018-09-19 13:45:17Z

2

You can use keyof operator:

type AddressKey = keyof Address

answered Sep 19, 2018 at 13:45

Aleksey L.

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