While grappling with this issue, the title question arose in my mind: How can I handle the situation where the library function getResponse returns { a: number } for Android phones and { b: number } for iOS phones?
The code snippet below initially led to a type error when assigning a value to value:
const response = getResponse();
const value = isAndroid ? response.a : response.b;
To address this, I implemented a type guard by defining a type predicate named isAndroidResponse
const isAndroidResponse = (
response: { a: number } | { b: number }
): response is { a: number } => {
return isAndroid; // 'response' parameter not used!
};
This type guard was then utilized as follows:
const response = getResponse();
let value;
if (isAndroidResponse(response)) {
value = response.a;
} else {
value = response.b;
}
Nevertheless, two concerns emerged regarding this solution, causing me to question its effectiveness for my problem:
The type predicate does not utilize the input
responsevariable.The implementation entails a considerable amount of code. Ideally, I would prefer a more concise approach, such as the following (which is invalid TypeScript syntax):
type ResponseT = isAndroid ? { a: number } : { b: number }; const response = getResponse(); const value = isAndroid ? response.a : response.b;
This leads me to my follow-up inquiry: Is leveraging a type predicate a viable solution, or am I misapplying it in this context?
I have also set up a TS playground showcasing the scenario described above.