Here is the current situation:
type A = { b: string, c: number }
I have an object that I will receive from an API, which could be either
A[] or []
As of now, when I attempt to use it,
const apiData: A[] || []
const b = apiData[0].a // I expected this to cause an error, but it doesn't.
How can I structure this in a way that would result in an error?
In my opinion, the most straightforward approach in this situation is to utilize Partial:
type A = { b: string, c: number }
type Obj = Partial<A[]>
declare var apiData: Obj;
const check = apiData[0] // A | undefined
Alternatively, you have the option to employ a typeguard
type A = { b: string, c: number }
type Obj = A[]
declare var apiData: Obj;
const isEmpty = <Elem,>(arg: Elem[]): arg is never[] => arg.length === 0
if (isEmpty(apiData)) {
const x = apiData[0] // never
} else {
const x = apiData[0] // A
}
Moving on to the next type definition
type Obj = A[] | never[]
This solution may not function as expected due to the fact that never[] extends A[]
type IsAssignable = never[] extends A[] ? true : false // true
Furthermore, you can enable the noUncheckedIndexedAccess flag
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