Extract values from deeply nested object structure

Question

I have a deeply nested object structure that contains other objects that all should have a value key, I'm trying to keep the object structure and replace the values with the type of values for each key. Now I've created a type Result that almost does what I need it to do, however, the created type also has an error.

T[key]['value'] - Type '"value"' cannot be used to index type 'T[key]'.(2536)

I'm also struggling with how to do it that if the value prop does not exist, it defaults to string

class A<T = string>{
    constructor(public value:T){}
}

const data = {
    propA: {value:'test'},
    nested:{
        propA: new A([123]),
        propBool: new A(123)
    }
}


type Replace<T, A extends {value:any}={value:any}> = T extends object
    ? { [key in keyof T]: T[key] extends {value:any}? T[key]['value'] : Replace<T[key], A> }
    : T;


type Result = Replace<typeof data> //ok

class A<T = string>{
    constructor(public value:T){}
}

const data = {
    propA: {value:'test'},
    nested:{
        propA: new A([123]),
        propBool: new A(123)
    }
}


type Replace<T, A extends {value:any}={value:any}> = T extends object
    ? { [key in keyof T]: T[key] extends {value:any}? T[key]['value'] : Replace<T[key], A> }
    : T;


type Result = Replace<typeof data>

// result
type Result = {
    propA: string;
    nested: {
        propA: number[];
        propBool: number;
    };
}

Typescript Playground

This looks exactly the same as stackoverflow.com/questions/67240685/…, so you can do the same thing - T[key]['value' & keyof T[key]] — Nadia Chibrikova
– Nadia Chibrikova, Commented Apr 24, 2021 at 13:59
@NadiaChibrikova Can you post this as the answer so I can accept it. — Ivan V.
– Ivan V., Commented Apr 26, 2021 at 18:49

Nadia Chibrikova · Accepted Answer · 2021-04-26 19:39:06Z

1

You can use an intersection type to affirm thatvalue is one of the fields of T[key]: T[key]['value' & keyof T[key]]

answered Apr 26, 2021 at 19:39

Nadia Chibrikova

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