CODEWITHSUNDEEP
typescript
Mary
Mary

Reputation: 1125

In TypeScript, why is my type aliasing returning errors?

In Car.ts, I have the following code:

export class Car {

    static SMALL: string = "small";
    static MEDIUM: string = "medium";
    static LARGE: string = "large";

}

In CarSize.ts, I have the following code:

import { Car } from "./Car";

type CARSIZE = Car.SMALL | Car.MEDIUM | Car.LARGE;

I'm trying to create a CARSIZE type which can only be one of Car.SMALL, Car.MEDIUM or CAR.LARGE.

I receive the following error:

'Car' only refers to a type, but is being used as a namespace here.

How do I fix this error?

Upvotes: 1

Views: 125

Answers (1)

Aleksey L.
Aleksey L.

Reputation: 37918

Because Car.SMALL is a value, not a type.

I'd use string enum in this case:

enum CarSize {
  small = "small",
  medium = "medium",
  large = "large"
}

But if you really want to get this working, you can use typeof to get the type of the value. Also you'll need to define properties as readonly and remove explicit type notation, so compiler will be able to infer the types as literals:

class Car {
    static readonly SMALL = "small";
    static readonly MEDIUM = "medium";
    static readonly LARGE = "large";
}

type CARSIZE = typeof Car.SMALL | typeof Car.MEDIUM | typeof Car.LARGE;

Upvotes: 4

Related Questions