Typescript: string literal types from interface parameters

Question

Let say I have an interface like this

interface I{
  id: string;
  name: string;
  age: number;
}

and a method like this

var obj:I={
      id: 'abc',
      name: 'Jim',
      age: 23
};
changeProperty(name:string, value:any){
   obj[name] = value;
}

Is there a way to declare the name parameter type to match interface fields?

One solution would be something like this

changeProperty(name: 'id' | 'name' | 'age' , value:any)

but in a much larger project where an interface can have 20+ fields it's much harder to maintain this.

unfortunately no as it will make type unsafe

Priyesh Kumar
– Priyesh Kumar

2017-05-22 16:31:47 +00:00
Commented May 22, 2017 at 16:31 — Priyesh Kumar
– Priyesh Kumar, Commented May 22, 2017 at 16:31

artem · Accepted Answer · 2017-05-22 16:39:14Z

5

Yes, as described in the example for keyof and lookup types:

function changeProperty<N extends keyof I>(name: N, value: I[N]){
   obj[name] = value;
}

changeProperty('id', '123'); // ok
changeProperty('age', 53); // ok
changeProperty('name', 1); // Argument of type '1' is not assignable to parameter of type 'string'

answered May 22, 2017 at 16:39

artem

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