Generic type 'BallInterface' requires 2 type argument(s)

Question

I am learning Typescript and I got this error Generic type 'BallInterface' requires 2 type argument(s) at tennisBall. How can I call the function whose parameter object has more than one generic type? Why is it throwing an error? The whole code:

const addId = <T extends object>(obj: T) =>{ 
    const id = 3;
    return {
        ...obj,
        id
    }
}

interface BallInterface<T, V>{
    name: string
    data: T
    meta: V
}

const ball: BallInterface<{meta: string}, string> = {
    name: "Tennis",
    data:{meta: "for playing"},
    meta: "Mario"
}

const tennisBall = addId<BallInterface>(ball);

Answer 1

It is throwing an error because you defined BallInterface as an interface that has two generics.

On the last line, you call addId you pass BallInterface as generic, without specifying what would T and V of BallInterface be.

It's not entirely clear what your goal is here. If all you want to achieve is to add the Id field, you don't need to pass a generic to addId at all. You're making it more difficult than what actually is :)

const addId = (obj: object) =>{ 
    const id = 3;
    return {
        ...obj,
        id
    }
}

interface BallInterface<T, V>{
    name: string
    data: T
    meta: V
}

const ball: BallInterface<{meta: string}, string> = {
    name: "Tennis",
    data:{meta: "for playing"},
    meta: "Mario"
}

const tennisBall = addId(ball);