Typescript type casting when destructuring

Question

Let's assume this

{foo, bar} = groupBy(arg);

I want to cast foo to type Foo and bar to type Bar. How can I do this?

I'm a complete beginner with Typescript. groupBy is the one from lodash package.

score 36 · Accepted Answer · answered Nov 26 '16 at 18:51

36

If Typescript can not deduce the type of the result of groupBy you could try asserting it yourself.

function groupBy(o: any) {
    return o; // return any
}

let x = { a: 1, b: "1" }

// we know better than tsc and assert the type
let {a, b} = <{ a: number, b: string }>groupBy(x);

answered Nov 26 '16 at 18:51

toskv

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Actually this is exactly what I was looking for! Thank you! – Alkis Kalogeris Nov 26 '16 at 20:00
you should also check out the duplicate from artem, it's got a cleaner solution. – toskv Nov 26 '16 at 20:43
4

This will not always work because more complex objects will cause TS2352 (insufficient type overlap). ie `const {target} = <{target: HTMLInputElement}>mouseEvent`. – Sjeiti Apr 22 '21 at 07:00

Typescript type casting when destructuring

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