I'm trying to make getResults
function return the proper type, but currently stuck with this:
interface IResponse<T> {
result: T;
}
type FnType<P, R> = (params: P) => R;
const r1: IResponse<string[]> = { result: ['123'] };
const r2: IResponse<number[]> = { result: [456] };
const getResults = <T, R extends IResponse<T[]>, P>(fn: FnType<P, R>, params: P): T[] => {
return [
...fn(params).result,
...fn(params).result
];
};
const getValue = <T>(r: IResponse<T>) => r;
// returned type is unknown[]
// how can we make it return string[]?
getResults(getValue, r1);
// returned type is unknown[]
// how can we make it return number[]?
getResults(getValue, r2);
The code is just an example, in the production getResults
function is used to merge results from a paginated request (fn
in this case is a request function)
CodePudding user response:
So, I'm not sure this will also cover the things you need for production. But the return type looks alright like this:
interface IResponse<T> {
result: T;
}
type FnType<P, R> = (params: P) => R;
const r1: IResponse<string[]> = { result: ['123'] };
const r2: IResponse<number[]> = { result: [456] };
const myResults = <P,R>(fn: FnType<P,IResponse<R[]>>, params: P): R[] => {
return [
...fn(params).result,
...fn(params).result
];
}
const getValue = <T>(r: IResponse<T>) => r;
myResults(getValue, r1);
myResults(getValue, r2);
Edit: I'm actually not exactly sure why the code in question does not give correct IntelliSense, it makes sense to me.
But what I can see is that you used three generic types T
, R
and P
. My Idea is that basically you only have 2 types to worry about which are params and the Result of the method.
I basically say, whatever type is inside the getValue
's IResponse
will be the final output of the myResults
function.