[英]Typescript: use ReturnType of array of functions (edited)
I am trying to type the following function:我正在尝试输入以下 function:
function foo(input, modifier, merge) {
return merge(...modifier.map(m => m(input)));
}
The objective is to have the correct types for the parameters of the merge
function.目标是为
merge
function 的参数提供正确的类型。
Context:语境:
modifier
is an array of function with a single parameter of the type of typeof input
and a different return type for each function modifier
是 function 的数组,具有typeof input
类型的单个参数和每个 function 的不同返回类型merge
is a function, which has modifier.length
parameters, with the parameter at position n having the same type as the return type of the function modifier[n]
and returns a singe (generic) value merge
是一个function,它有modifier.length
参数,在position n处的参数与function的返回类型具有相同的类型)值modifier[n]
How can this be done?如何才能做到这一点?
Possible with objects ( Record<K,V>
):可以使用对象(
Record<K,V>
):
// for Functions (here type Func)
type Func = () => any;
// a mapping of a string key to an function can be created
type FuncMap = Record<string, Func>;
// for this mapping you can create a mapping to the return types of each function
type ReturnTypeMap<T extends FuncMap> = { [K in keyof T]: ReturnType<T[K]> }
Is something like this also possible for arrays, based on the position instead of a object key?基于 position 而不是 object 密钥的 arrays 是否也可以进行类似的操作?
This is my attempt at the typing the function, but i don't know how to use ReturnType in combination with arrays:这是我尝试输入 function,但我不知道如何将 ReturnType 与 arrays 结合使用:
function foo<I, M extends Array<(input: I) => any>, O>(
input: I,
modifier: M,
merge: (...args: ReturnType<M>) => O
// ^^^^^^^^^^^^^ this is not working, since relation to each item is missing
): O {
return merge(...modifier.map(m => m(input)));
}
Do it like this I think:这样做我认为:
type ExtractReturnTypes<T extends readonly ((i: any) => any)[]> = [
... {
[K in keyof T]: T[K] extends ((i: any) => infer R) ? R : never
}
];
function foo<I, M extends readonly ((i: I) => any)[], O>(
input: I,
modifiers: M,
merge: (...args: ExtractReturnTypes<M>) => O
) {}
foo(
1,
[(i: number) => 5, (i: number) => 'b' as const] as const,
// a has type: number
// b has type: 'b'
(a, b) => 'test'
);
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