TypeScript: Getting names (as string) of Union's possible types?

Question

Is it possible to get names of Union's possible types?

Given that I have defined these interfaces and type aliases:

// https://basarat.gitbook.io/typescript/type-system/discriminated-unions

interface Square {
    kind: "square";
    size: number;
}

interface Rectangle {
    kind: "rectangle";
    width: number;
    height: number;
}

type Shape = Square | Rectangle;

Can I get a union of string like this?

type ShapeName = 'Square' | 'Rectangle';

score 2 · Answer 1 · answered Jan 25 '21 at 14:38

2

You can do smth like that:

interface Square {
  kind: "square";
  size: number;
}

interface Rectangle {
  kind: "rectangle";
  width: number;
  height: number;
}

type Shape = Square | Rectangle;

type ShapeName = Shape['kind'] // 'square' | 'rectangle';

Please keep in mind, you are unable to obtain interface name unless you map some how it.

answered Jan 25 '21 at 14:38

captain-yossarian from Ukraine

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> _you are unable to obtain interface name_ – I see. Then I have to use a property like `kind` in the example, right? Thank you! – ayumitamai97 Jan 25 '21 at 14:46
Right, you should use `kind` in this case – captain-yossarian from Ukraine Jan 26 '21 at 06:57

TypeScript: Getting names (as string) of Union's possible types?

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