Typescript 接口 object 按键

Question

How in typescript create interface of array of key value pair from another interface keys.

typescriptlang sandbox

A have next interfaces:

type KeyValue<K, V> = {
    key: K;
    value: V;
};

interface Features {
    wheels: number;
    color: string;
    packages?: string[];
}

interface Car {
    manufacturer: string;
    model: string;
    features: Features;
}

Next, create variables using this interfaces:

const fordFocus: Car = {
    manufacturer: "ford",
    model: "focus",
    features: {
        wheels: 17,
        color: "white",
    },
};

const bmwX3: Car = {
    manufacturer: "bmw",
    model: "X3",
    features: {
        wheels: 19,
        color: "black",
        packages: ["S08SM", "S08TF", "S08TG", "S0925"],
    },
};

I want to send this variables to server.

Request data should have next schema:

interface CarRequest {
    manufacturer: string;
    model: string;
    features?: {key: string, value: any}[]
}

Now i declare features manually, but i want to do it by utility interface. Like this:

interface FeaturesRequest<T, K in T> {
  [n: number]: {key: K, value: T}
}

Function that prepare request data

function prepareCarRequest(car: Car) {
    const request: CarRequest = {
        manufacturer: car.manufacturer,
        model: car.model,
        features: Object.entries(car.features).map(([key, value]) => ({key, value})),
    };

    return request;
}

I don't understand how i should declare requestData that it pick keys in Feature interface and transform it to KeyValue automatically.

Answer 1

You can transform your interface into key-value type with a rather simple mapped type :

type InterfaceToKV<T> = {
    [K in keyof T]: { key: K, value: T[K] }
}[keyof T]

TS playground

But the Object.entries ' type is more generic (discussion is about Object.keys but the same applies to Object.entries ) and will not allow you to assign string to your key literal types.