Interface members to validate string variables

Issue

Let's say, I have an interface like this:

interface field {
    code: string
    name: string
    // ...
}

Then I want to create a variable with a value that only accepts members from that interface:

let key: "code" | "name" // ...

It will be a very wide line of code if there are many interface members, is there a solution for this?

Is there a quick solution to validate a variable based on the members of the interface using TypeScript as above?

Solution

That is the use case for the keyof type operator:

The keyof operator takes an object type and produces a string or numeric literal union of its keys.

interface field {
    code: string
    name: string
    // ...
}

let key: keyof field;

key = "code"; // Okay
key = "other"; // Type '"other"' is not assignable to type 'keyof field'.

Playground Link

Answered By - ghybs